1913. Christian Literature Society of India: London, Madras, and

Calcutta. JOURNALS. For current researches the following, among others, should be consulted:-- _Annals of Tropical Medicine and Parasitology_, Liverpool. _Annales de l’Institut Pasteur_, Paris. _Archives de Parasitologie_, Paris. _Archives de Zoologie Expérimentale et Générale_, Paris. _Archiv für Protistenkunde_, Jena. _Archiv für Schiffs- und Tropen-Hygiene_, Leipzig. _Bulletin of Entomological Research_, London. _Bulletin de l’Institut Pasteur_, Paris. _Bulletin de la Société de Pathologie Exotique_, Paris. _Bulletins of the Bureau of Animal Industry_, Washington. _Centralblatt für Bakteriologie und Parasitenkunde_, Jena. _Compt. Rend. Acad. Sci._, Paris. _Compt. Rend. Soc. Biol._, Paris. _Indian Journal of Medical Research_, Calcutta. _Journal of Experimental Medicine_, New York. _Journal of Medical Research_, Boston. _Memorias do Instituto Oswaldo Cruz_, Rio de Janeiro. _Parasitology_, Cambridge. _Proceedings of the Royal Society_, London. _Quarterly Journal of Microscopical Science_, London. _Review of Applied Entomology_, London. _Tropical Diseases Bulletin_ (London: Tropical Diseases Bureau). _Zeitschrift für Infektionskrankheiten_, Berlin. THE ANIMAL PARASITES OF MAN. Man is one of those organisms in on on which a whole host of parasites find conditions suitable for their existence: Protozoa, Platyhelminthes, Nematoda, Acanthocephala, Hirudinea, and a large number of Arthropoda (Arachnida as well as Insects) all include members which are parasites of man. These animals either live on the external surface of the body or within the intestine and its appendages. Other organs and systems are not quite free from foreign organisms--we are acquainted with parasites in the skeletal system, in the circulatory system, in the brain, in the muscles, in the excretory and genital organs, and even in the organs of sense. It is possible, and perhaps might be advantageous, to arrange and describe the parasites of man according to the situations in which they are found (parasites of the skin, intestinal parasites, etc.). Their description in the various stages of development would, however, be disturbed when, as is generally the case, the different stages are passed in different organs, and a work which treats more fully of the natural history of the parasites than of the local disorders to which they give rise would suffer thereby. It is, therefore, preferable to describe the parasites of man in their systematic order, and to mention their different situations in man in describing each species. A. *PROTOZOA*, BY H. B. FANTHAM, M.A., D.Sc. All those animal organisms which throughout their entire life never rise above the unicellular stage, or merely form simple, loose colonies of similar unicellular animals, are grouped under the term _Protozoa_ (Goldfuss, 1820), as the simplest types of animal life. All the vital functions of these, the lowest forms of animals, are carried out by their body substance, the protoplasm (sarcode). Often particular parts possess special functions, but the limits of a cell are never over-stepped thereby. These special parts of the cell are called “cell-organs”; recently they have been termed “organellæ.” The living protoplasm has the appearance of a finely granular, viscid substance which, as a rule, when not surrounded by dense investing membranes or skeletons, exhibits a distinct kind of movement, which has been termed amœboid. According to the species, processes of different forms and varying numbers called pseudopodia are protruded and withdrawn, and with their assistance these tiny organisms glide along--it might almost be said flow along--over the surface. In most Protozoa two layers of cytoplasm may be recognised, and distinguished by their appearance and structure, namely, the superficially situated, viscid, and quite hyaline ectosarc or ectoplasm, and the more fluid and always granular endosarc or endoplasm, which is entirely enveloped by the ectoplasm. The two layers have different functions; the movements originate from the ectoplasm, which also undoubtedly fulfils the functions of breathing, introduction of food and excretion. The endoplasm, which in some forms (Radiolaria) is separated from the ectoplasm by a membrane, undertakes the digestion of the food. To this distribution of functions between the various layers of cytoplasm is due the development of particular cellular organs, such as the appearance of cilia, flagella, suctorial tubules (in the Suctoria) and the myophan striations, which are contractile parts of the ectoplasm in Infusoria and Gregarines. In many cases (Flagellata, Ciliata), an area is differentiated for the ingestion of food (oral part, cytostome) to which there is often added a straight or curved opening (cytopharynx), through which the food reaches the endoplasm. The indigestible residue is either cast off through the oral part or excreted by a special anal part (cytopyge). In rare cases, structures sensitive to light, the so-called pigment or eye spots are developed, _e.g._, _Euglena_. In the case of Infusoria the endoplasm circulates slowly, and agglomerations of fluids (food vacuoles) sometimes appear around each bolus of food; in these vacuoles the food is digested under the action of certain materials (ferments). Even in the lowliest Protozoa fluids to be excreted are, as a rule, gathered into one, or, more rarely, several contractile vacuoles, which regularly discharge their contents. This action, however, is to a certain extent governed by the temperature of the surrounding medium. In some Infusoria a tube-like channel in the cytoplasm is joined to the contractile vacuole which usually occupies a certain position; this forms a sort of excretory duct, and there are also supply-canals leading to these organellæ. Very frequently various substances are deposited in the endoplasm, such as fatty granules, drops of oil, pigment granules, bubbles of gas or crystals. More solid skeletal substances are secreted in or on the ectoplasm. To the latter belong the cuticle of the Sporozoa and Infusoria, the chalky shells containing one or several chambers of the Foraminifera, the siliceous and very ornamental framework of the Radiolaria, and the chitinous coat of many Flagellata, Infusoria, etc. Some forms make use of foreign bodies found in their surroundings, such as grains of sand, to construct their protective coverings. The food often consists of small animal or vegetable organisms and of organic waste; it is usually introduced _in toto_ into the endoplasm. On the other hand, the Suctoria extract nourishment from their prey by means of their tentacles. Many parasitic species also ingest solid food, others feed by endosmosis. In all cases one nucleus at least is present. It is true that the existence of non-nucleated Protozoa, the so-called _Monera_, is still insisted upon, but some of these have already proved to be nucleated, and the presence of nuclei in the others will no doubt be established. Very often the number of nuclei increases considerably, but these multinucleate stages are always preceded by uninucleate stages. In the Infusoria, in addition to the larger or principal nucleus (macronucleus) there is usually a smaller reproductive nucleus (micronucleus). This dualism of the nuclear apparatus is considered by some to be general, and usually to appear first at the onset of reproduction. The form and structure of the nucleus vary greatly in different species. There are elongate, kidney-shaped, or even branched nuclei as well as spherical or oval ones. In addition to vesicular nuclei with a distinct karyosome and incidentally also with a nuclear membrane, homogeneous and more solid formations are frequently encountered. The nuclei are always differentiated from the protoplasm by their reactions, particularly in regard to certain stains. In many Protozoa an extra-nuclear mass, sometimes compact, sometimes diffuse, arises from or near the nucleus. This mass, whose staining reactions resemble those of the nucleus, is termed the chromidial apparatus. On the dualistic hypothesis, two varieties of chromidia occur, one originating from the vegetative nucleus (macronucleus), being chromidia in the restricted sense, the other derived from the reproductive or micronucleus being termed sporetia. Chromidia consist of altered (? katabolic) nuclear material. The nucleus plays the same part in the life of the single celled organisms as it does in the cells of the Metazoa and Metaphyta. It appears to influence in a certain manner all, or at least most, of the processes of life, such as motility, regeneration, growth, and generally also digestion. Its principal influence, however, is exercised in the propagation of the cells, as this is always brought about by the nucleus. The PROPAGATION of the Protozoa is effected either by division or by means of direct budding. In division, which is preceded by direct or indirect (mitotic) division of the nucleus, the body separates into two, several, or even a great many segments. In this process the entire substance of the body is involved, or a small residual fragment may be left, which does not undergo further division and finally perishes. In the budding method of multiplication a large number of buds are formed, either on the surface or in the interior of the organism. Where divisions or buddings follow one another rapidly, without the segments separating immediately after their production, numerous forms develop, which are often unlike the parental forms, and these are termed swarm spores or spores. Divisions imperfectly accomplished lead to the formation of protozoal colonies. Sometimes encystment[9] takes place previous to division. Frequently, also, sexual processes appear, such as the union of two similar (isogamous) or dissimilar (anisogamous) individuals. In the latter case sexual dimorphism occurs, with the formation of males (microgametes) and of females (macrogametes). The union may be permanent (copulation), the process being comparable with the fertilisation of the ovum by a spermatozoon. On the other hand, attachment may be transient (conjugation) when, after the exchange of portions of the nucleus, the couple separate, to multiply independently of each other. Sometimes there is an ALTERNATION OF GENERATIONS, as there may be several methods of propagation combined in the same species, either direct multiplication, conjugation, or copulation being practised; the different generations may thus, in certain cases, be unlike morphologically. [9] Independently of propagation, many protozoa protect themselves from death by encystment when the water in which they are living dries up; in this condition the wind may carry them over wide tracts of land. Protozoa inhabit salt water as well as fresh water; they are also found on land in very damp places, and invade animals as parasites. CLASSIFICATION OF THE PROTOZOA. _Class I._--*Sarcodina* (_Rhizopoda_). Protozoa, the body substance of which forms pseudopodia; many of them are capable of developing chitinous, chalky, or siliceous coverings or skeletal structures, which, however, permit the protrusion of the pseudopodia either over the entire periphery or at certain points. They possess one nucleus or several. _Order 1._--_Amœbina_ (Lobosa) naked or with a simple shell, sometimes formed of a foreign substance; the pseudopodia may be lobose or finger-shaped; there may be a contractile vacuole; generally only one nucleus. They live in fresh or salt water, in the soil, and also parasitically. _Order 2._--_Foraminifera_ (Reticularia). Mostly provided with a calcareous shell, usually consisting of several chambers, and allowing the protrusion of the pseudopodia either at the periphery or only at the opening. The pseudopodia are filamentous and frequently anastomosed; there is no contractile vacuole; there are usually several nuclei. Mostly marine. _Order 3._--_Heliozoa._ Naked, or with a chitinous or simple radial siliceous skeleton; the pseudopodia are filamentous, and are frequently supported by firmer axes, which exhibit no tendency to anastomosis; there is a contractile vacuole; one or several nuclei. Live in fresh water. _Order 4._--_Radiolaria_. The body has radially-disposed filamentous pseudopodia, and the nucleus is hidden in the central capsule; there is almost always a siliceous framework, consisting of pieces arranged radially, tangentially, or lattice-like; there is no contractile vacuole, but fluid-containing hydrostatic vacuoles are present in the peripheral protoplasm. Marine. _Class II._--*Mastigophora* (_Flagellata_). Protozoa with one or several long flagella used for locomotion and for acquiring food; in stationary forms their only function is to take in food. Cytostome and contractile vacuole may be present. May be either naked or provided with protective coverings; one or more nuclei. They live either in fresh or salt water, or may be parasitic. This class is again divided into several sub-classes and orders, of which only the Euflagellata, with the Protomonadina and Polymastigoda are of interest here. _Class III._--*Sporozoa.* Protozoa that only live parasitically in the cells, tissues, or organs of other animals. They ingest liquid food by osmosis; the surface of the body is covered with an ectoplasmic layer, or cuticle; they have no cilia in the adult state, but may form pseudopodia. Flagella occur, but only on the male propagating individuals. There may be one or numerous nuclei, but no contractile vacuole. Propagation by means of spores, mostly provided with sporocysts, is characteristic. _Sub-class_ 1.--*Telosporidia.* These are usually of constant form, rarely amœboid; they are uninucleate in the mature state; they live within host cells in the first stage. Spore-formation occurs at the end of the life-cycle. _Order 1._--_Gregarinida._ Body of a constant, usually elongate form, surrounded by a cuticle. In the early stage they lead an intracellular existence; in the mature stage they live within the intestine or body cavity of invertebrate animals, especially the Arthropoda, and, like intestinal parasites, are provided with clinging organs. Copulation usually isogamous; the spores have coats (chlamydospores) and usually contain several minute germs (sporozoites). _Order 2._--_Coccidiidea._ Body of uniform spherical or oval shape: they lead an intracellular life, but are not freely motile in cavities of the body. Fertilization is anisogamous; the spores have coats or shells (sporocysts), and usually contain several sporozoites. Exhibit alternation of generations. _Order 3._--_Hæmosporidia._ Parasites of the blood corpuscles of vertebrate animals; they exhibit amœboid movement; fertilization is anisogamous; many present alternation of generations and hosts; spores naked. _Sub-class 2._--*Neosporidia.* They are multinucleate when adult, and the form of the body varies exceedingly (often amœboid); spore-formation commences before the completion of growth. _Order 1._--_Myxosporidia._ The spores have valvular coats, with or without caudal appendages, with two, rarely four, polar capsules. They live free in such organs as the gall or urinary bladder, but are chiefly found in connective tissue. They occur especially in fishes. _Order 2._--_Microsporidia._ Spores with coats or sporocysts; no caudal appendage, with one polar capsule. They usually live in the tissues of Arthropoda. _Order 3._--_Sarcosporidia._ Elongate parasites of the muscular fibres of amniotic vertebrates, on rare occasions they occur also in the connective tissue; the spores, which are kidney or sickle-shaped, are naked and apparently have no obvious polar capsule. _Order 4._--_Haplosporidia._ Simple organisms, forming simple spores; they occur in Rotifers, Polychætes, Fish and Man. _Class IV._--*Infusoria* (_Ciliata_). The body is generally uniform in shape, with cilia and contractile vacuole, frequently also with cytostome; usually has macro- and micro-nucleus; live free in water and also parasitically. The orders _Holotricha_, _Heterotricha_, _Oligotricha_, _Hypotricha_ and _Peritricha_ are classified according to the arrangement of the cilia. _Class V._--*Suctoria.* Bodies with suctorial tubes, contractile vacuoles, macro- and micro-nucleus, no cytostome. They generally invade aquatic animals as cavity parasites, yet also attack plants; early stage ciliated. Live sometimes as parasites on Infusoria. [The Suctoria are frequently regarded as a sub-class of the Infusoria.] The Protozoa and Protophyta are sometimes united under the term _Protista_ (Haeckel, 1866). The Spirochætes are Protists (see pp. 114–128). Class I. *SARCODINA*, Bütschli, 1882. Order. *Amœbina*, Ehrenberg. A. *Human Intestinal Amœbæ.* The first record of the occurrence of amœba-like organisms in the human intestine, that is, in intestinal evacuations, was that of Lambl (1859); nevertheless, the case was not quite conclusive, as the occurrence of testaceous amœbæ of fresh water (_Arcella_, _Difflugia_) was also reported. In 1870 Lewis found amœbæ associated with disorders of the large intestine in patients in Calcutta. A year later Cunningham reported from the same locality that he had observed on eighteen occasions, in one hundred examinations of dejecta from cholera patients, colourless bodies with amœboid movements, which became encysted and multiplied by fission. The daughter forms were said to be capable of dividing again, but they might also remain in contact. Contractile vacuoles were not noticed. The same bodies were observed also in simple diarrhœa (twenty-eight cases out of one hundred.) [Illustration: FIG. 1.--_Amœba coli_, Lösch, in the intestinal mucus. (After Lösch.)] The case reported by Lösch in 1875 attracted more attention. It was that of a peasant, aged 24, who came from the province of Archangel. He was admitted into Eichwald’s clinic at Petrograd with symptoms of dysentery. In the discharges containing blood and pus, Lösch found amœbæ in large numbers. When at rest these amœbæ measured from 20 µ to 35 µ; in a state of movement their length might extend up to 60 µ (fig. 1). The pseudopodia appeared only singly, and, since they were hyaline (ectoplasmic), were thus distinguished from the markedly granular endoplasm that enclosed a spherical nucleus of from 5 µ to 7 µ in diameter. One or more non-contractile vacuoles were present. Quinine enemata had the effect of making the amœbæ disappear from the fæces and thus causing the diarrhœa to abate. Four months after admission the patient died from the results of intercurrent pneumonia. At the autopsy ulceration of the large intestine was found, especially in the lower parts. Lösch connected the amœbæ with the ulcerations by experiments made on four dogs by injecting them with recently passed stools (_per os et anum_). Eight days after the last injection numerous amœbæ were found in the fæces of one of these dogs; eighteen days after the injection the animal was killed. The mucosa of the rectum was inflamed, covered with blood-stained mucus and ulcerated in three places. Numbers of amœbæ were found both in the pus of the ulcers and in the mucus. The three other dogs remained healthy. From these observations Lösch concluded that the species of amœba described by him as _Amœba coli_ could not be regarded as the primary cause of the disease, but that it was certainly capable of increasing a lesion of the large intestine already present, or at least of preventing its healing. B. Grassi (1879) found in the stools of healthy as well as in those of diarrhœic patients from various localities in Northern Italy, amœbæ similar to those discovered by Lösch. As this was of frequent occurrence, the pathogenicity could not be definitely established. Normand, formerly naval surgeon at Hong-Kong, observed numerous amœbæ in the dejecta of two patients suffering from colitis. Many further investigations, which cannot be quoted in detail, showed not only that intestinal amœbæ were widely distributed in man, but indicated with greater certainty their rôle as agents of dysentery. The Commission sent out by the German Government in the year 1883 to investigate cholera in India and Egypt--whose members discovered the cholera bacillus--also collected information with regard to dysentery. In five cases of dysentery examined _post mortem_ at Alexandria, with the exception of one case in which ulceration of the colon had already cicatrized or was approaching cicatrization, R. Koch found amœbæ as well as bacteria in sections from the base of the ulcers, although such had previously escaped notice in examination of the dejecta. Encouraged by these results, Kartulis (1885), who had discovered amœba-like bodies in the stools of patients suffering from intestinal complaints at Alexandria, continued his investigations. The results, obtained from more than 500 cases, gave rise to the theory that typical dysentery was caused by amœbæ as were also the liver-abscesses that often accompany it. Kartulis supported his theory not only by the regular occurrence of amœbæ in the stools of dysenteric patients and their absence in other diseases, and by the occurrence of the parasites in ulcers of the large intestine and in the pus from liver-abscesses, but also by experiments which he performed on cats. These were infected by injection _per anum_ of stool material rich in amœbæ from subjects of dysentery. The infection took place also when amœba-containing, but bacteria-free, pus from liver-abscesses was used. It has been objected that the infection of man with _Amœba coli_, as the dysenteric amœbæ were then generally designated, does not take place _per anum_ but _per os_. This difficulty, however, diminished in proportion as the encysted states of amœbæ (fig. 2), long known in the case of other Protozoa, became understood. The infection of man (Calandruccio, 1890) and of cats (Quincke and Roos) succeeded solely when material containing such stages was used. Amœbæ introduced into the intestine multiply there by fission (Harris, 1894). However, this theory, to which various other authors gave support on the grounds of their own observations, encountered opposition. Thus it was established that amœbæ were not found in patients in every place where dysentery was endemic, or else they were much rarer than was expected. Further, amœbæ were present in the most varied kinds of intestinal diseases, both of infective and non-infective characters. Also they were present in quite healthy persons. Moreover, for various reasons, infection experiments on animals failed to supply proof, and finally a bacterium was discovered (Shiga, 1898) to be the excitant of one form of dysentery. Agglutination attested the specific part played by this organism, as it was produced by the blood serum of a person suffering from or recovered from dysentery, but not by the serum of one who was uninfected. Bacillary dysentery consequently was a distinct entity. The final step to be taken was to decide whether there was a specific amœbic enteritis (amœbic dysentery or amœbiasis, according to Musgrave). [Illustration: FIG. 2.--Encysted intestinal amœbæ showing nuclear multiplication. (After B. Grassi.)] This question should decidedly be regarded from the positive point of view. It is intimately connected with another, namely, whether there are not several species of intestinal amœbæ. The possibility of this had already been recognized. In addition to the _Amœba coli_ Lösch, R. Blanchard distinguished yet another, _Amœba intestinalis_, and designated thereby the large amœbæ described in the first communication made by Kartulis; later on he stated the distinction between the species. Councilman and Lafleur[10] (1891) considered the amœba of dysentery to be _Amœba coli_ Lösch and so re-named the species _Amœba dysenteriæ_. Kruse and Pasquale (1893) employed the same nomenclature, but retained the old name _Amœba coli_ Lösch for the non-infectious species. Quincke and Roos (1893) set forth three species: a smaller species (25 µ) finely granular, pathogenic for men and cats (_Amœba coli_ Lösch); a larger species (40 µ) coarsely granular, pathogenic for men but not for cats (_A. coli mitis_); and a similar species non-pathogenic either for man or cat (_A. intestini vulgaris_). Celli and Fiocca (1894–6) went still further, they distinguished: (1) _Amœba lobosa_ variety _guttula_ (= _A. guttula_ Duj), variety _oblonga_ (= _A. oblonga_ Schm.) and variety _coli_ (= _A. coli_ Lösch). (2) _Amœba spinosa_ n. sp. occurring in the vagina as well as in the intestine of human patients suffering from diarrhœa and dysentery. (3) _Amœba diaphana_ n. sp. found in the human intestine in cases of dysentery. (4) _Amœba vermicularis_ Weisse, present in the vagina and in dysentery; and (5) _Amœba reticularis_ n. sp. in dysentery. [10] “Amœbic Dysentery,” _Johns Hopkins Hosp. Repts._, ii, pp. 395–548, 7 plates. Shiga distinguished two species; a larger pathogenic species with a somewhat active movement, and a small harmless species with a somewhat sluggish movement. Bowman mentions two varieties, Strong and Musgrave (1900) two species--the pathogenic _Amœba dysenteriæ_ and the non-pathogenic _Amœba coli_; Jäger (1902) and Jürgens (1902) mention at least two species. In the following year (1903) a work by Schaudinn was published which marked a real advance. This, in conjunction with the establishing of a special genus (_Endamœba_ or _Entamœba_) for human intestinal amœbæ first by Leidy[11] and then by Casagrandi and Barbagallo,[12] for the time cleared up the confused nomenclature, the old name _Amœba coli_ being retained for the harmless intestinal amœbæ of man, whereas the pathogenic species was designated _Entamœba histolytica_. The history of more recent work is incorporated in the accounts of the entamœbæ given below. [11] “On _Amœba blattae_,” _Proc. Acad. Nat. Sci._, Philadelphia (1879), xxxi, p. 204. [12] “_Entamœba hominis_ s. _Amœba coli_ (Lösch).” _Annali d’Igiene speriment._ (1897), vii, p. 103. See also further remarks on p. 34. *Entamœba coli*, Lösch, 1875, emend. Schaudinn, 1903. Syn.: _Amœba coli_, Lösch, 1875. _Entamœba hominis_, Casagr. et Barbag. 1897. The amœboid trophozoite, according to Lösch, measures 26 µ to 30 µ and upwards; according to Grassi 8 µ to 22 µ; according to Schuberg 12 µ to 26 µ. A separation of the body substance into ectoplasm and endoplasm is only perceived during movement. The pseudopodia, which are generally only protruded singly, are broad and rounded at the end (lobopodia) and are hyaline, while the remainder of the body is granular. The ectoplasm is less refractile than the rest of the cytoplasm; it also stains less intensely (fig. 1), and is best seen on protrusion of a pseudopodium. Red blood corpuscles are rarely, if ever, found ingested in the cytoplasm. [Illustration: FIG. 3.--_Entamœba coli_: life-cycle, _a_-_e_, stages in binary fission; _A_-_D_, schizogony, with formation of eight merozoites; 2–10, cyst formation or sporogony, with formation of eight nucleate cysts. (After Castellani and Chalmers)] The nucleus is vesicular, and is spherical when inactive, measuring 5 µ to 7 µ, with a thick nuclear membrane. In the centre of the nucleus is a chromatinic body or karyosome or sometimes several small nuclear bodies formed of plastin and chromatin; the remaining chromatin is arranged on the achromatic network in the form of fine granules, especially thickly deposited on the nuclear membrane. _Entamœba coli_ lives as a commensal in the upper portion of the large intestine, where the fæces still possess a pulpy consistency. With their concentration and change in reaction lower in the bowel, the parasites either die or else if they are at a suitable stage of development form resistant cysts. These cysts (fig. 2) can be found in great abundance in normal fæces, as Grassi first observed. Slight laxantia or intestinal diseases of any kind producing increased peristalsis, however, show amœbæ even in the unencysted condition, provided that the person harbours intestinal amœbæ generally. The intensity of infection varies according to the locality; thus Schaudinn found that 50 per cent. of the persons examined were infected with harmless amœbæ in East Prussia, 20 per cent. in Berlin and about 66 per cent. on the Austrian littoral. The life-history (fig. 3) of the parasite exhibits two phases: (_a_) asexual multiplication in the intestine, either by binary fission or by schizogony with formation of eight merozoites, and (_b_) sporogony leading to the production of eight-nucleate cysts. Infection results from ingestion of cysts. Only cysts with eight nuclei are infective. The diameter of such cysts is about 15 µ to 20 µ. There are varying accounts of the details of the life-cycle of _Entamœba coli_ in its different stages. Thus, regarding schizogony or multiple fission it was formerly stated that the nucleus of the parent amœba divided into eight portions, which after dissolution of the nuclear membrane, passed outwards into the cytoplasm, which segregated around each. Eight merozoites were thus produced. More recently the process of schizogony has been considered to consist in the repeated division of the nucleus into two, four, and finally eight nuclei (fig. 3, A-D), and the formation of eight merozoites or amœbulæ. The process of encystment is initiated by the extrusion of all liquid and foreign bodies from the protoplasm, which assumes a spherical form (fig. 4, A). The rounded uninucleate amœba then secretes a soft gelatinous coat, which finally differentiates into a double contoured cyst wall in older cysts. According to Casagrandi and Barbagallo, the size of the cyst varies from 8 µ to 30 µ, and averages about 15 µ. According to Schaudinn (1903) the cytological changes during cyst formation are as follows. The nucleus of a rounded uninucleate form divides into two (fig. 4, B). Each of these nuclei fragments into chromidia (fig. 4, C), some of which are absorbed, while others reunite so that the cell becomes binucleate again. Each of these nuclei, by a twice repeated division, produces three nuclei (fig. 4, D), the smaller two of which degenerate and were regarded as reduction nuclei. There is a clear zone or vacuole in the middle of the cyst during these maturation processes, dividing the cyst into two halves. After the nuclear reduction the clear space disappears, and each nucleus (termed by some a gamete nucleus) divides into two pronuclei (fig. 4, E). The pronuclei of the pairs were said by Schaudinn to differ slightly. Copulation occurs between pairs of unlike pronuclei, and is an example of autogamy (fig. 4, F). When complete, each of the fusion nuclei (synkarya) divides twice, giving rise first to four and finally to eight nuclei. Eight amœbulæ are thus formed within the cyst. According to Hartmann and Whitmore (1911)[13], however, autogamy does not occur within the cysts of _E. coli._ They consider that eight small amœbulæ are formed (fig. 3, _2_-_10_) which escape from the cyst and then conjugate in pairs (fig. 3, _10_-_12_), afterwards growing into a new generation of trophozoites. [13] _Archiv f. Protistenkunde_, xxiv, p. 182. Only some 10 to 20 per cent. of the cysts evacuated with the fæces undergo the full course of development, the majority perish previously. In old dry fæces, only cysts with eight nuclei are found, and it is these alone that cause the infection. _Entamœba williamsi_, _E. bütschlii_, _E. hartmanni_ and _E. poleki_ (Prowazek) are probably only varieties of _E. coli_. [Illustration: FIG. 4.--So-called autogamy of _Entamœba coli_. A, rounded amœba; B, nucleus dividing; C, the two daughter-nuclei giving off chromidia; D, each nucleus has formed two reduction nuclei; E, cyst membrane formed, and gamete nuclei are dividing; F, cyst with two synkarya.] The principal feature distinguishing _Entamœba coli_ from _E. histolytica_ is the formation of eight-nucleate cysts by the former as contrasted with the tetra-nucleate cysts of the latter. The cyst-wall of _E. coli_ is thicker than that of _E. histolytica_ (_tetragena_). Further, _E. coli_ does not usually ingest red blood corpuscles, nor are “chromidial blocks” present inside its cyst (see p. 40). According to Chatton and Lalung-Bonnaire[14] (1912) the entamœbæ of vertebrates should be placed in a separate genus _Löschia_, as they differ in their life-history from _E. blattæ_, the type species of _Entamœba_. Leidy (1879), however, named the genus _Endamœba_, but further researches are necessary on biological variation among these organisms. [14] _Bull. Soc. Path. Exotique_, v, p. 135. *Entamœba histolytica*, Schaudinn, 1903. Syn.: _Amœba coli_, autt. p. p. _Amœba dysenteriæ_, autt. p. p. The average size of the amœboid trophozoite is 25 µ to 30 µ. In fæces diluted with salt solution the amœbæ swell to 40 µ and more. There is sometimes separation of the body substance into a strongly refractile vitreous ectoplasm and a corneous endoplasm, pronounced even in repose, although the former is not equally thick at all parts of the periphery. In the endoplasm generally there are numerous foreign bodies (bacteria, epithelial cells, colourless and red blood corpuscles (fig. 6), and occasionally living flagellates of the intestine). The nucleus is 4 µ to 6 µ in diameter, and may be difficult to recognize because it is sometimes weakly refractile and poor in chromatin. Its shape is slightly variable; it is usually excentric, sometimes wholly peripheral at the limit of the two parts of the body. Vacuoles are not present in quite fresh specimens, but appear later. In the study of _E. histolytica_, the morphological characters of the trophozoite or vegetative stage of the organism formerly separated as _E. tetragena_ (figs. 5, 6, 8_a_) must be considered (see p. 38). [Illustration: FIG. 5.--_Entamœba histolytica_ (_tetragena_ form), showing three successive changes of form due to movement. × 1100. (After Hartmann.)] The history of the development of these species, which give rise to amœbic enteritis as distinguished from bacillary dysentery, was formerly not so well known as that of _E. coli_. Upon being introduced into cats (_per anum_) dysenteric amœbæ provoke symptoms similar to those in man. In the latter, besides metastatic liver abscesses, abscesses of the lungs, and, according to Kartulis, cerebral abscesses are occasionally produced. Marchoux (1899) states that when the disease has lasted for some time liver abscesses are produced in cats also. [Illustration: FIG. 6.--_Entamœba histolytica_ which has ingested many red blood corpuscles. × 1100. (After Hartmann.)] [Illustration: FIG. 7.--Section through wall of large intestine (of a man) close under an ulcer caused by _Entamœba histolytica_. A, amœbæ that have penetrated partly in blood-vessels (Bv), partly in tissue of submucosa to the muscularis. Magnified. (After Harris.)] In the large intestine of infected cats the amœbæ creep over the epithelium, and here and there they force the epithelial cells apart, as well as removing them or pushing them in front of them; the amœbæ thus insert themselves into the narrowest fissures. They penetrate also into the glands through the epithelium, and thence into the connective tissue of the mucosa. Intestinal and glandular epithelia perish under the influence of these parasites: the cells are pushed aside, fall to pieces or are absorbed by the amœbæ. In the connective tissue of the mucosa the amœbæ migrate further, and often accumulate above the muscles. Finally they rupture this and force their way into the submucosa. In cats, apparently, the penetration is not so great as in men, according to Kruse and Pasquale. During their migration the parasites also gain access to the lymph-follicles of the wall of the intestine, which become swollen and commence to suppurate; follicular abscesses arise and after their rupture follicular ulcers. The diseased patches in the mucosa are markedly hyperæmic and numerous hæmorrhages are set up. Roos and Harris state that the amœbæ also penetrate into the blood-vessels (fig. 7) and this explains the occurrence of metastatic abscesses.[15] The whole submucosa is severely swollen at the diseased spot and undergoes small-celled infiltration in the neighbourhood of the colonies of amœbæ. From these findings Jürgens (1902) draws the conclusion[16] which is followed here, that the amœbæ are causative agents of the enteritis of cats, which disease is well defined, both pathologically and anatomically. Subsequent researches confirm the experience of earlier authors; great precautions were taken to exclude errors, hence, as with Gross and Harris, no exception can be taken to their results. The inoculation material was derived from soldiers who suffered from amœbic enteritis in China and who were admitted into the garrison hospital at Berlin. In order to be independent of the patients themselves, transmission experiments from cat to cat were performed, after the first experiments on cats yielded positive results. This was also effected by rectal feeding as employed by earlier workers. Such appeared necessary in order to prevent the evacuation of the inoculation material _per anum_, as well as to avoid the employment of morphia and ether narcosis. Forty-six cats were used for the experiments. Ten cats received tested stools containing motile amœbæ from soldiers suffering from amœbic enteritis contracted in China. Sixteen other cats received stools from cats infected by inoculation. All the animals sickened and suffered from the disease. Five cats received dejecta from human amœbic enteritis in which, however, no _motile_ amœbæ were present. Thirteen cats received stools from soldiers who suffered from bacillary dysentery. None of the latter cats took the complaint and none showed changes in the large intestine upon sectioning. The injection of various bacteria, obtained from a stool of amœbic enteritis pathogenic to cats, remained without result in both the cats employed for this experiment. Lastly, two cats, which had been kept with those artificially infected, were taken ill spontaneously and suffered from the disease. In the opinion of Harris, who ascertained the harmless nature of bacteria derived from the intestinal flora containing dysenteric amœbæ, young dogs are capable of being infected. [15] Lung abscesses generally arise by the bursting of a liver abscess through the diaphragm into the right lower lobe of the lung, sometimes also through conveyance of amœbæ by means of the blood-stream (Banting). [16] These findings were confirmed by Schaudinn by means of investigations on cats and men. _Cf._ also Alfred Gross, Marchoux, P. G. Woolley, W. E. Musgrave, H. F. Harris and others. Within the large intestine an active increase of _Entamœba histolytica_ must occur. Nevertheless, Jürgens did not definitely find changes that might be interpreted in this sense. Schaudinn (1903) observed division and gemmation _in vivo_. Both processes, in which the nucleus divides by amitosis, can only be distinguished by the fact that the daughter individuals are similar in binary fission but dissimilar in gemmation, whether they make their appearance singly or in greater numbers. Schizogony, resulting in the formation of eight individuals, which is so characteristic for _Entamœba coli_, was not observed. (But schizogony, into four merozoites, is now known to occur. Gemmation processes are apparently degenerative.) Resistant stages, which serve for transmission to other hosts, are according to Schaudinn[17] first formed when the diseased portions commence to heal, or more accurately, the recovery commences when the vegetative increase of the amœbæ in the intestine discontinues. The so-called spores of _E. histolytica_ were distinguished very definitely from those of _E. coli_; they were said to consist of spheres of only 3 to 7 µ in diameter, which were surrounded by a double membrane, at first colourless, but becoming a light brownish yellow colour after a few hours, and possessing a protoplasmic content containing chromidia. They were said to arise by fragments of chromatin passing outwards from the nucleus of the amœba into the surrounding cytoplasm (fig. 9, _a_) and undergoing so marked an increase that finally the whole cytoplasm became filled with chromidia. The remainder of the nucleus underwent degeneration and became extruded. On the surface of the cytoplasm there then arose small protuberances containing chromidia. These processes had been observed in the living organisms. They gradually divided and separated from membranes which later became yellow. The remainder of the amœba perished. Craig[18] had also seen phases of this process of development. It must be remarked that, according to recent researches, these processes of exogenous sporulation are degenerative in character (see p. 41). The small spores may be fungi. The “sporulation” processes are only mentioned here as a warning. They are now only of historic interest. By means of an experiment made on a cat, Schaudinn ascertained that ingestion of permanent cysts, which resist desiccation, is the cause of the infection. The animal took food containing dry fæces with amœba cysts; these fæces came from a patient suffering from amœbic enteritis in China. On the evening of the third day the cat evacuated blood-stained mucous fæces which contained large numbers of typical _Entamœba histolytica_. On the fourth day after the infection the animal experimented upon died, and the large intestine showed the changes previously stated. [17] _Arb. a. d. kaiserl. Gesundheitsamte_, xix, pp, 547–576. [18] “Life cycle of _Amœba coli_ in Human Body,” _American Medicine_, 1904, vii, p. 299; viii, p. 185. _E. histolytica_ also is found in the large intestine. This was originally shown to be the case by Kartulis, and the fact has recently been confirmed from many quarters. It is also present in the metastatic abscesses of which it is the cause (_cf._ among other authors, Rogers, _Brit. Med. Journ._, 1902, ii, No. 2,177, p. 844; and 1903, i, No. 2,214, p. 1315). It should lastly be pointed out in this connection that mixed infections also take place. For instance, in addition to _E. histolytica_, _E. coli_, and, under certain circumstances, flagellates may be found together. In the same way _E. coli_ may come under observation even in bacillary dysentery. On the other hand, Schaudinn stated that in cases of dysentery endemic in Istria, _Entamœba coli_, if it had hitherto been present, disappeared, to return again after recovery from the illness. [Illustration: FIG. 8.--_Entamœba histolytica_. _a_, trophozoite (_tetragena_ type) containing red blood corpuscles, × 1,300; _b_ and _c_, two isolated nuclei showing different appearances of karyosome, centriole and nuclear membrane, × 2,600. (After Hartmann.)] (_Entamœba tetragena_, Viereck, 1907.) This amœba must now be considered to be a part of the lifecycle of _Entamœba histolytica_, in fact a very important part of that cycle, especially in its tetranucleate cystic stages. This organism, the so-called _Entamœba tetragena_, may occur in the human intestine in cases of amœbic dysentery, especially in mild or chronic cases. It was discovered by Viereck in 1907 in patients suffering from dysentery contracted in Africa. Soon afterwards an independent description was published by Hartmann, who called the amœba _E. africana_. It was also studied by Bensen and Werner. Recently (1912–13) much work has been published on this amœba by Darling and others; in this way its relationship to Schaudinn’s _E. histolytica_ has been made known. In general morphology it somewhat resembles _Entamœba coli_, and its discoverer at first mistook it for a variety of that species. According to Hartmann, a distinct ectoplasm is only clearly visible when a pseudopodium is protruded (fig. 5). The granular endoplasm may contain ingested red blood corpuscles (fig. 6). The large, round nucleus is visible in the fresh state (fig. 8, _a_). So-called chromidial masses (? crystalloidal substances) may occur in the cytoplasm. [Illustration: FIG. 9.--_Entamœba histolytica_ (_tetragena_ form). _a_, emission of chromatin from nucleus; _b_, nuclear division; _c_, degenerating form with two nuclei; _d_, _e_, _f_, cysts containing one, two and four nuclei respectively, and showing chromidial blocks. × 2,000. (After Hartmann.)] Some investigators, as Hartmann,[19] lay stress on the internal structure of the nucleus (fig. 8, _b_, _c_), best seen in preparations fixed wet and stained with iron-hæmatoxylin. The nucleus is limited by a well-marked nuclear membrane, on the inside of which granules or nodules of chromatin may occur. There is a karyosome, which, in successfully stained specimens, shows, at times, a central dot called a centriole. (The nucleus of _Entamœba coli_ does not contain such a centriole.) However, the structure of the nucleus varies at different periods during the life-cycle. [19] _Arch. f. Protistenkunde_ (1911), xxiv, p. 163. The diameter of the trophozoites or vegetative forms (fig. 8, _a_) is variously given as from 20 µ to 40 µ. Multiplication proceeds by binary fission and also by schizogony into four merozoites.[20] [20] _See_ Darling, 1913, _Arch. Intern. Med._, vol. ii, pl. i, fig. 3. Reproduction takes place by endogenous encystment (fig. 9, _d_-_f_), which is preceded by nuclear division into two, reduction and then autogamy. The interpretation of the latter phenomenon as autogamy is disputed by some authors. The round cysts, which may measure 12 µ to 15 µ in diameter, contain four nuclei, together with darkly staining masses of various shapes, the so-called “chromidial blocks” (fig. 9, _f_). The cyst-wall of _E. histolytica_ (_tetragena_) is thinner than that of _E. coli_, and the diameter of the cyst is rather less. _E. histolytica_ has not yet been cultivated. Infection in man occurs by way of the mouth by the ingestion of cysts. A patient showing acute symptoms of dysentery is not usually infective, for he is merely harbouring the large trophozoites, which, by experiment, have been shown not to be infective to animals (kittens) when administered by the mouth. The stools of recovered patients may still contain cysts, and they may thus act as cyst-carriers or reservoirs of disease by infecting water and soil. The stools of such cyst-carriers are often solid, and so cysts of _E. histolytica_ (_tetragena_) are easily overlooked. Mathis (1913)[21] points out that healthy carriers of _E. histolytica_ may be found; 8 per cent. of the natives of Tonkin examined by him were healthy carriers of cysts. [21] _Bull. Soc. Med. et Chirurg. Indo-Chine_, iv, p. 474. In return cases, or prolonged untreated cases of entamœbic dysentery, a generation of smaller trophozoites is associated with, or replaces the larger ones. In stools they are frequently refractile and consequently stain slowly _intra vitam_. These trophozoites are the “smaller, senile, or pre-cyst generation” of Darling. This pre-cyst generation is characterized by the presence of blocks of crystalloidal substance in the cytoplasm, and by the possession of a prominent, densely stainable karyosome. Darling believes this generation to be the same as that described by Elmassian as _Entamœba minuta_.[22] [22] _Centralbl. f. Bakter._, Orig., lii, p. 335. Walker,[23] Darling,[24] Wenyon[25] and others believe that _Entamœba histolytica_, which was only seen by Schaudinn in a single case, that of a Chinaman, is really _E. tetragena_. Darling states that if the published illustrations of _E. histolytica_ and of _E. tetragena_ are collected from the literature and compared, it will be seen that the writers have been calling _E. histolytica_ the large trophozoites seen in dysenteric stools. These large trophozoites frequently display no karyosome, but they can be demonstrated as _E. tetragena_ by animal inoculation, or by the history of the case. On the other hand, the illustrations of _E. tetragena_ show that the authors have been dealing with the small generation or reduced forms (“_E. minuta_”), which are the direct descendants of the large trophozoites. If kittens are inoculated rectally with dysenteric material containing large trophozoites, the strain may be carried in successive kittens for four to six transfers. If, on the other hand, kittens are inoculated rectally with small trophozoites of the pre-cyst generation, the transmission cannot be carried through more than one or two kittens. Wenyon has succeeded in maintaining _E. tetragena_ in kittens for several generations. [23] _Philip. Journ. Sc._ (1911), B, vi, p. 259. [24] _Annals Trop. Med. and Parasitol._ (1913), vii, p. 321. [25] _Brit. Med. Journ._, Nov. 15, 1913, p. 1287, and _Journ. Lond. School Trop. Med._, ii, p. 27. In some of the preparations from the last remove, pathological forms of the trophozoites may be seen. These show abnormal forms of budding, especially peripherally, such as have been described by Schaudinn and by Craig as characteristic of _E. histolytica_. Schaudinn’s small peripheral, exogenous buds and cysts are thus explained. Craig has latterly changed his views. Further, Darling states that _tetragena_ cysts fed by the mouth to kittens produce bowel lesions in which trophozoites having the characters of _E. tetragena_, _E. histolytica_ and _E. nipponica_ (Koidzumi) occur. In view of the work of recent observers, the peculiar exogenous encystment which Schaudinn made characteristic of _Entamœba histolytica_ has been shown to be due to degenerative changes in senile races of the amœba. _E. histolytica_ and _E. tetragena_ are one and the same species, and its trophozoite is subject to variation. According to some observers the _histolytica_ type of nucleus--described by Schaudinn as being poor in chromatin and not easily seen in the fresh state--occurs frequently in patients with severe symptoms of dysentery; on the other hand, the _tetragena_ type of nucleus--round and easily seen in the fresh state--may occur in cases presenting slight dysenteric symptoms. Intermediate types of nuclei are seen. The name of this species, the principal pathogenic amœba of man, must then be _E. histolytica_ by priority. The cystic stages of _E. histolytica_ are those first recorded by Viereck and formerly described as _E. tetragena_. The geographical distribution of _E. histolytica_ is wide. *Noc’s Entamœba* (1909). A species of Entamœba was cultivated by Noc[26] in 1909 from cysts derived from liver abscesses, from dysenteric stools and from the water supply of Saigon, Cochin China. He cultivated it in association with bacteria. It is pathogenic. It has been considered allied to _E. histolytica_, and shows internal segmentation or schizogony. It exhibits polymorphism. This amœba has been found by Greig and Wells (1911) in cases of dysentery in India. It is an important organism and requires further investigation. [26] Noc, F. (1909), _Ann. Inst. Pasteur_, xxiii, p. 177. Certain other Entamœbæ[27] have been described at various times from the intestinal tract of man. Probably most, if not all, of these are not good species and in some cases much more information is needed. [27] See Fantham, H. B. (1911), _Annals Trop. Med. and Parasitol._, v, p. 111. _Entamœba tropicalis_ (Lesage, 1908). This parasite is said to be non-pathogenic, and to occur in the intestine of man in the tropics. It has a general resemblance to _E. coli_, but forms small cysts (6 µ to 10 µ in diameter). The nucleus of the cyst is said to break up into a variable number of daughter nuclei, from three to thirteen having been noted. Lesage states that it is culturable in symbiosis with bacteria. It is probably a variety of _E. coli_, if not a cultural amœba. _Entamœba hominis_ (Walker, 1908) has a diameter of 6 µ to 15 µ. A contractile vacuole is present. Encystment is total, and small cysts are formed. It is culturable. The original strain, now lost, was obtained from an autopsy in Boston Hospital. This organism is probably a cultural amœba. _Entamœba phagocytoides_ (Gauducheau, 1908). This parasite was discovered in a case of dysentery at Hanoi, Indo-China. The amœba is small, 2 µ to 15 µ in diameter. It is active. It ingests bacteria and red blood corpuscles, while peculiar spirilla-like bodies are found in its cytoplasm. It multiplies by binary and multiple fission. It can be cultivated. More recently (1912) the author appears to consider the amœba to be a stage of a _Trichomonas_, but abandons the view later (1914). Further researches on this organism are needed. _Entamœba minuta_ (Elmassian, 1909)[28] was found, in association with _E. coli_, in a case of chronic dysentery in Paraguay. It resembles _E. tetragena_ but is smaller, rarely exceeding 14 µ in diameter. Schizogony occurs, four merozoites being produced. The encystment is total and endogenous, giving rise to cysts containing four nuclei. This amœba is considered by Darling and others to be the pre-cyst trophozoite stage of _E. histolytica_ (_tetragena_). [28] _Centralbl. f. Bakter._, Orig., lii, p. 335. _Entamœba nipponica_ (Koidzumi, 1909) was found in the motions of Japanese suffering from dysentery or from diarrhœa, in the former case in company with _Entamœba histolytica_. Its diameter is 15 µ to 30 µ. The endoplasm is phagocytic for red blood corpuscles. The nucleus is well defined, resembling that of _E. coli_ and of _E. tetragena_. Multiplication occurs by binary fission and by schizogony. Encystment is total, but has not been completely followed. Darling and others consider that this is an abnormal form of _E. histolytica_, while Akashi (1913) doubts if it is an amœba at all, but rather is to be regarded as shed epithelial cells. GENERAL REMARK.--It is now considered by some workers that true Entamœbæ cannot be cultivated on artificial media. Quite recently Williams and Calkins (1913)[29] have somewhat doubted this opinion, and state that certain cultural amœbæ, originally obtained from Musgrave in Manila, exhibit the various morphological variations associated with true entamœbæ of the human digestive tract. [29] _Journ. of Med. Research_, xxix, p. 43. *Entamœba buccalis*, Prowazek, 1904. The size varies from 6 µ to 32 µ. Ectoplasm is always present; the endoplasm contains numerous food-vacuoles. The nucleus is vesicular, with a greenish tinted membrane which is poor in chromatin. The size of the nucleus is from 1·5 µ to 4·5 µ. A contractile vacuole is not visible. The pseudopodium is broad. It was discovered in the mouths of persons with dental caries at Rovigno and also at Trieste, being most easily found in dense masses of leucocytes, also among leptothrix and spirochæte clusters. It can be easily distinguished from leucocytes by more intense staining with neutral red. Multiplication proceeds by fission. Transmission may take place through the small spherical cysts. This species (fig. 10) has since been observed in Berlin, and is also occasionally found in carcinoma of various regions of the oral cavity. (Leyden and Löwenthal, 1905). [Illustration: FIG. 10.--_Entamœba buccalis_, Prow. _a_-_d_, the same specimen observed during five minutes. × 1,000. _e_, amœba fixed and stained with iron-hæmatoxylin. × 1,500. (After Leyden and Löwenthal.)] _Entamœba buccalis_, Prow., is said to be allied to a protozoön which A. Tietze has found either encysted or free in the lumen of the orifice of the parotid gland of an infant aged 4 months. The gland had undergone pathological change, and had therefore been extirpated. The organisms, which were roundish and three to four times the size of the normal epithelial cells of the gland, were without a membrane and possessed a nucleus in which the chromatic substance appeared to be contained in a karyosome. Bass and John’s[30] (Feb. 1915) and Smith, Middleton and Barrett (1914) state that _E. buccalis_ is the cause of pyorrhœa alveolaris. [30] _Journ. Amer. Med. Assoc._, lxiv, p. 553. _Entamœba undulans_, Aldo Castellani, 1905. Under this name a protozoön is described which A. Castellani found in addition to _Entamœba histolytica_ and _Trichomonas intestinalis_ in the fæces of an European planter living in Ceylon, who had suffered from amœbic enteritis and liver abscess. The shape of the body was roundish or oval, 25 µ to 30 µ in the greatest diameter. It was without a flagellum, but with an undulating membrane, and capable of protruding a long pseudopodium from different parts of its body at short intervals. The nucleus could not always be recognized in life; it was, however, always demonstrable by staining. One or two contractile vacuoles were present. The protoplasm was finely granular, showing no differentiation into ecto- and endo-plasm. According to Braun, in spite of the author declaring himself expressly against the flagellate nature of the parasite, such a nature may be assumed to be tolerably certain in view of the description and illustration. It is now considered that _Entamœba undulans_ is a portion of a flagellate, namely, _Trichomonas_. *Entamœba kartulisi*, Doflein, 1901. Doflein gave this name to amœbæ, from 30 µ to 38 µ in diameter, which Kartulis (1893) found on examining the pus of an abscess in the right lower jaw of an Arab, aged 43, and in a portion of bone that had been extracted. The movements of the amœbæ (fig. 11) were more active than those of “dysenteric amœbæ.” Their coarsely granular cytoplasm contained blood and pus corpuscles, and a nucleus was generally only recognizable after staining. Vacuoles were not seen with certainty. Flexner reported upon a similar case, and Kartulis published five additional cases. As in these cases dental caries was present the infection is likely to have proceeded from the oral cavity as a result of the carious teeth. Craig[31] (1911) considers that this parasite is probably identical with _Entamœba histolytica_. [31] “The Parasitic Amœbæ of Man,” Lippincott, Philadelphia. [Illustration: FIG. 11.--_Entamœba kartulisi_, Dofl., from the pus of an abscess in the lower jaw, showing different stages of movement. (After Kartulis.)] In the literature the following species have been reported as occurring in the oral cavity of man:-- _Amœba gingivalis_, Gros, 1849. [? identical with _Entamœba buccalis_.] _Amœba buccalis_, Sternberg, 1862. _Amœba dentalis_, Grassi, 1879. Far too little, however, is known concerning these to regard them as definite species, that is, independent organisms; Grassi thinks it even possible there may have been a confusion in their case with salivary corpuscles. If they really are amœbæ they are all of them probably identical with _Entamœba buccalis_. Genus *Paramœba*, Schaudinn, 1896. Schaudinn established the genus _Paramœba_ for a marine rhizopod which multiplied by division, became encysted at the end of its vegetative life and then segmented into swarm bodies with two flagella. These multiplied by longitudinal fission, and finally passed into the condition of Amœbæ. Whether the human parasite described by C. F. Craig (1906) as *Paramœba hominis.* belonged to this genus was for a time uncertain. It is now placed in a new genus Craigia, Calkins, 1912, since it possesses only one flagellum.[32] [32] See Craig (1913), _Amer. Journ. Trop. Dis. and Prevent. Med._, i, p. 351. In the amœbic stage it is 15 µ to 25 µ in diameter; ecto- and endo-plasm during rest are indistinguishable. The body substance is granular, with a spherical, sharply contoured nucleus and an accessory nuclear body. No vacuoles are present, but occasionally the endoplasm contains red blood corpuscles. The pseudopodia are hyaline, finger- or lobe-shaped, and are protruded either singly or in twos. Multiplication is by binary fission and by the formation of spherical cysts (15 µ to 20 µ in diameter) in which occurs successive division of the nuclei, ultimately forming ten to twelve roundish bodies each of which soon develops a flagellum. The flagellate stages have similarly a spherical shape and attain a diameter of 10 µ to 15 µ. They also occasionally contain red blood corpuscles and pass either directly or after longitudinal division into the amœboid phase. Craig found these Amœbæ and the flagellate stage belonging to them in six patients in the military hospital at Manila (Philippine Islands), five of whom were suffering from simple diarrhœa whilst the sixth exhibited an amœbic enteritis and contained also _Paramœba hominis_, with _Entamœba histolytica_, Schaudinn. In one of the other cases, _Trichomonas intestinalis_ was present. B. *Amœbæ from other Organs.* *Entamœba pulmonalis*, Artault, 1898. Artault[33] discovered a few amœboid forms with nucleus and vacuole in the contents of a lung cavity. In the fresh condition they were distinguishable from leucocytes by their remarkable capacity of light refraction. They were also much slower than the latter in staining with methylene blue or fuchsine. Their movements became more lively in a strong light. Water and other reagents killed them, and then, even when stained, they could not be distinguished from leucocytes. They have also been seen by Brumpt. R. Blanchard found amœbæ which may belong here in the lungs of sheep. _A. pulmonalis_ is perhaps the same as _Entamœba buccalis_. Smith and Weidman[34] (1910, 1914) described an entamœba, _E. mortinatalium_, from the lungs and other organs of infants in America. [33] _Arch. de Parasitologie_, i, p. 275. [34] _Amer. Journ. Trop. Dis. and Prevent. Med._, ii, p. 256. *Amœba urogenitalis*, Baelz, 1883. This species was found in masses in the sanguineous urine as well as in the vagina of a patient in Japan, aged 23. Shortly before the death of the patient, which was caused by pulmonary tuberculosis, hæmaturia with severe tenesmus of the bladder had set in. The amœba, which showed great motility, and had a diameter of about 50 µ when quiescent, exhibited a granular cytoplasm and a vesicular nucleus. Baelz is of opinion that these parasites were introduced into the vulva with the water used for washing the parts, and thence had penetrated into the bladder and vagina. Doflein places the organism in the genus _Entamœba_, and it is perhaps identical with _E. histolytica_. Similar cases are also reported (1892–3) by other authors: Jürgens, Kartulis, Posner, and Wijnhoff. Jürgens found small mucous cysts, filled with amœboid bodies, in the bladder of an old woman suffering from chronic cystitis; they were also found in the vagina. The amœba observed by Kartulis in the sanguineous urine of a woman, aged 58, suffering from a tumour of the bladder, measured 12 µ to 20 µ, and exhibited slow movements by protruding short pseudopodia. The vacuoles and nucleus became visible only after staining with methylene blue. Posner’s case related to a man, aged 37, who had hitherto been quite healthy and had never been out of Berlin. Suddenly, after a rigor, he passed urine tinged with blood. This contained, besides red and white blood corpuscles and hyaline and granular casts, large granular bodies (about 50 µ in length and 28 µ in breadth), which slowly altered their shape, and contained red blood corpuscles in addition to other foreign matter. These bodies exhibited one or several nuclei and some vacuoles. From the course of the disease, which extended over a year, and during which similar attacks recurred, Posner came to the conclusion that the amœbæ which had originally invaded the bladder had penetrated into the pelvis of the kidney, where they probably had settled in a cyst, and thence induced the repeated attacks. Wijnhoff observed four cases of amœburia in Utrecht. *Amœba miurai*, Ijima, 1898. [Illustration: FIG. 12.--_Amœba miurai_, Ij. × 500. _a_, fresh; _b_, after treatment with dilute acetic acid. (After Ijima.)] Under this term the author describes protoplasmic bodies which Miura, in Tokyo, found in the serous fluid of a woman, aged 26, who had died from pleuritis and peritonitis endotheliomatosa. Two days before death these same forms had also appeared in the hæmorrhagic fæces of the patient. The bodies were usually spherical or ellipsoidal, and at one pole carried a small protuberance (fig. 12) beset with filamentous short “pseudopodia” (really a pseudopodium covered with cilia). Their size varied between 15 µ and 38 µ. The cytoplasm was finely granular, and no difference was observable in the ecto- and endo-plasm, only the villous appendage was clearer. The cytoplasm contained vacuoles more or less numerous, none of which was contractile. After the addition of acetic acid one to three nuclei could be distinguished, 8 µ to 15 µ in size. Actual movements were not observed. Taking everything into consideration, the independent nature of these bodies is, to say the least, doubtful, although it cannot be denied that they possess a certain similarity to the marine _Amœba fluida_, Grüber or Greeff, and to a few other species. (It is likely that cells present in serous exudation were mistaken for amœbæ.) APPENDIX. “_Rhizopods in Poliomyelitis acuta._” In three cases of poliomyelitis acuta which were investigated by Ellermann, the spinal fluid obtained by puncture of the cord contained bodies, from 10 µ to 15 µ in size, which had amœboid movements and exhibited variously shaped pseudopodia in large numbers. After staining, a usually excentric nucleus, about 1·5 µ in size, was demonstrated in them. Order. *Foraminifera*, d’Orbigny. The order is divided by Max Schultze into Monothalamia and Polythalamia. Only a few of the former can be considered here. Sub-Order. *Monothalamia.* (Testaceous Amœbæ). These forms occur frequently in fresh water, rarely in sea water. They possess a shell which is either pseudo-chitinous in character, or consists of foreign particles, or in a few cases is composed of siliceous lamellæ. There is usually an orifice for the protrusion of pseudopodia. The only representative of the order of interest here is:-- Genus. *Chlamydophrys*, Cienkowski, 1876. The genus is based on a form which A. Schneider carefully investigated and considered to be the _Difflugia enchelys_ of Ehrenberg. L. Cienkowski rediscovered this same form and created for it the genus _Chlamydophrys_. We agree with this view, but not with the renaming of the organism (so common at the time). If the parasite in dung, _Chlamydophrys stercorea_ Cienk. is identical with _Difflugia enchelys_ of Ehrenberg, the old specific name should be retained. The genus is characterized by the possession of a hyaline, structureless, slightly flexible shell which is ovoid or reniform. At the more pointed pole there is an orifice situated terminally or somewhat laterally, serving for the emergence of the filiform pseudopodia (fig. 13, _a_). The protoplasm does not entirely fill the interior of the shell. An equatorial zone bearing excretory granules divides the shell internally into two almost equal portions. The anterior portion is rich in vacuoles and serves for the reception of nutriment and for digestion. The posterior part is vitreous, and contains the nucleus. One to three contractile vacuoles are situated in the equatorial zone. *Chlamydophrys enchelys*, Ehrbg. Syn.: _Chlamydophrys stercorea_, L. Cienkowski. This species (fig. 13) is found in the fæces of various animals (cattle, rabbits, mice, and lizards), and also in quite fresh human fæces. According to Schaudinn, the parasite occurs so frequently in the human fæces that it must be considered of wide distribution. The species must traverse the intestine of man and animals during one stage of its life cycle, as Schaudinn showed by experiments on himself and on mice. He infected himself with cysts (fig. 14) by swallowing them, and evacuated the first _Chlamydophrys_ as early as the following day. After the evacuation of numerous specimens on one of the following days the infection ceased. The nucleus of a living specimen is surrounded by a hyaline, strongly refractile chromidial mass, arranged in the form of a ring. Chromatin stains colour it darkly. _Asexual multiplication_ (fig. 13, _b_), which takes place in fæces, follows a similar course to that of allied forms (_e.g._, _Euglypha_, _Centropyxis_). It commences by the cytoplasm issuing from the orifice of the shell and assuming the shape characteristic of the mother organism, but in a reverse position. The nucleus then divides by mitosis, when the daughter nuclei move apart from one another. The chromidial ring also divides into two portions by a process of dumb-bell like constriction. The one daughter nucleus remains in the mother organism, the other moves towards the daughter individual, which then separates from the parent. [Illustration: FIG. 13.--_Chlamydophrys enchelys._ _a_, free, motile form, showing nucleus, equatorial granules, vacuoles and pseudopodia; _b_, dividing organism. × 760. (After Cienkowski.)] In this species plasmogamic union of two or more individuals (up to twenty) is frequently observed. Such colonies may similarly divide, and in this way monstrosities frequently arise. When drying of the fæces, or deficiency of food occurs, encystment takes place apparently spontaneously. The whole body, as stated by Cienkowski, issues from the shell, assumes a spherical shape (probably with discharge of water) and becomes surrounded with a thick membrane (fig. 14). After the addition of water and the escape of the encysted _Chlamydophrys_, a new shell must be formed. Schaudinn, who has not given a more detailed description of the process of encystment in this species, but refers to Cienkowski and to similar observations made on _Centropyxis_, states of the latter that the encystment takes place within the shell. The _sexual multiplication_ is accompanied by shedding of all the foreign bodies and of the degenerating nucleus. The protoplasm, now contracting into a sphere, remains behind in the shell with the chromidial mass. From the latter several new nuclei arise (sexual nuclei) often eight in number. The cytoplasmic sphere then segregates into as many spherical portions as there are nuclei present. When they have assumed an oval form, two flagella develop at one pole and the flagellispores swarm out of the shell.[35] The biflagellate swarm-spores, or gametes, copulate in pairs and apparently the individuals of the pairs of gametes arise from different mother organisms. The zygote secretes a thick covering which soon becomes brown and rough. These zygote cysts or resistant spores must now pass from the intestine of an animal in order to complete their development. The escape of the cyst contents does not always take place in the intestine; often it does not occur until after defæcation. These shell-less individuals (amœbulæ) soon become invested with a shell. But in the alkaline intestinal contents, shell formation may proceed even while the organism is in the intestine, and multiplication may take place. [35] Schaudinn (1903), _Arb. a. d. Kaiserl. Gesundh._, xix, p. 547. [Illustration: FIG. 14.--_Chlamydophrys enchelys_, encysted; on the left the old capsule. × 760. (After Cienkowski.)] Schaudinn’s further communication was of special interest; it was to the effect that _Chlamydophrys_ was related to *Leydenia gemmipara*, Schaudinn, 1896. In the fluid removed by puncture from two patients suffering from ascites in the first medical clinic in Berlin, cellular bodies with spontaneous movement were found, which Leyden and Schaudinn regard as distinct organisms. They remained alive without the use of the warm stage for four or five hours, the external temperature being 24° to 25° C. In a quiescent condition they were of a spherical or irregular polygonal form. Their surface was rarely smooth, being beset with protuberances and excrescences (fig. 15). The substance of the body was thickly permeated with light refractile granules with a yellowish shimmer. The hyaline ectoplasm was rarely seen distinctly. All sizes from 3 µ to 36 µ in diameter were observed. The movements were rather sluggish, the ectoplasm in the meantime appearing in the form of one or several lamellæ, in which also strings of the granular endoplasm occurred, and frequently protruded over the border of the hyaline pseudopodia. The tendency for the joining of several individuals by means of their pseudopodia was so marked that associations ensued similar to those known in free-living Rhizopoda. The cytoplasm enclosed blood corpuscles as well as numerous vacuoles, one of which pulsated slowly about every quarter of an hour. A vesicular nucleus the diameter of which was about equal to one-fifth of the body was present. Multiplication took place by means of division and budding (fig. 15, _c_), after previous direct division of the nucleus. The buds were supposed to divide repeatedly soon after their appearance, thus giving rise to minute forms of 3 µ. There was a suspicion in both cases that the ascites was associated with malignant neoplasms in the abdomen, and autopsy confirmed this view in one case. [Illustration: FIG. 15.--_Leydenia gemmipara_, Schaud. _a_, in a quiescent condition, × 1000; _b_, in the act of moving, × 1000; _c_, from a fixed preparation, showing a bud, × 1500.] The parasite, which has seldom been observed, has been variously interpreted; for example, it has been regarded merely as altered tissue cells. It is now known, from Schaudinn’s researches, that _Leydenia gemmipara_ is connected with abnormal conditions of _Chlamydophrys_, occasionally occurring as a commensal in the ascitic fluid. The form is produced when pathological conditions of the large intestine create an alkaline reaction of its whole contents. The formation of shells then often ceases, and these naked _Chlamydophrys_ are enabled to multiply atypically by division and gemmation. Such stages, which are no longer capable of a normal development, are the _Leydenia_, as Schaudinn has demonstrated. Class II. *MASTIGOPHORA*, Diesing. Sub-Class. FLAGELLATA, Cohn emend. Bütschli. During the motile part of their life the Flagellata possess one or more flagella which serve for locomotion, and in many cases also for the capture of food. A few groups (_Euglenoidinæ_, _Choanoflagellata_) have only one flagellum, others two or several of about equal length (_Isomastigoda_), or of various lengths (_Monadina_, _Heteromastigoda_, _Dinoflagellata_). The long flagellum is the principal one; the smaller ones on the same organism are accessory flagella. The flagella directed backwards, which occur in the Heteromastigoda and are used for clinging, are termed trailing flagella or tractella. At the base of the flagellum, which is almost always at the anterior end, a Choanoflagellate possesses a cytoplasmic funnel-shaped neck or collar. In the parasitic forms an undulating membrane is often present. The body of the Flagellata is usually small, generally elongate and of unchangeable form. It is frequently covered by a distinct cuticle, and, in certain groups, by a hard envelope, or it may be more or less loosely enveloped by a gelatinous or membranous covering. An ectoplasmic layer is thin and not always obvious. The granular cytoplasm contains a varying number of vacuoles, one of which may be contractile, and is generally situated near the area from which the flagella arise, that is, at the anterior extremity. The cytoplasm, moreover, contains the nucleus, which is nearly always single; and in many species there are also yellow, brown, or green chromatophores of various shapes, such as occur in plants. Some species feed after the manner of green plants (holophytic), or of plants devoid of chlorophyll (saprophytic); others, again, ingest solid food, and for this purpose usually possess a cytostome; the latter, however, in a few forms is not used for its original function, but is connected with the contractile vacuole. Many parasitic forms feed by endosmosis. A few species possess eye-spots with or without light-refracting bodies. Variation in the form of the nuclear apparatus occurs. One nucleus only, which may be compact or vesicular, is known in many species. This nucleus is situated either centrally or sometimes near the flagellar end of the body, but its position is subject to variation. The flagella may arise near the nucleus. Other structures, such as an axial filament and a rhizoplast, may be present. Some flagellates are binucleate, the two nuclei--which often differ in size and shape--being separated from each other. One of these nuclei is the principal, vegetative or trophic nucleus; the other is an accessory nucleus, frequently termed the blepharoplast, flagellar or kinetic nucleus. One or more small basal granules are often present at or very near the origin of the flagella. Multiplication is by fission, usually longitudinal, which may occur in either the free or encysted forms. Division is initiated by that of the nucleus or nuclei (especially the kinetic nucleus). The basal granule divides also. Collars and chromatophores, if present, likewise separate into two. Variation in the method of doubling the original number of flagella occurs. In most organisms, especially uniflagellate forms, the flagellum splits lengthwise, after division of the basal granule, blepharoplast and nucleus. The daughter flagella may be of the same or different lengths and thicknesses. Other flagellates at division are said to produce new flagella in the neighbourhood of the original ones. The daughter organisms in such cases are provided with one or more parental flagella in addition to newly formed ones. It has been stated that in certain cases the parent flagellate retains all its flagella, while new ones arise _ab initio_ in the cytoplasm of the daughter forms. Multiplication by longitudinal fission may be interrupted sooner or later by the production of gametes, which form zygotes, from which new generations of individuals arise. In many flagellates gamete formation and sporogony are unknown, and asexual reproduction by fission alone prevails. Incomplete division results in the formation of colonies of individuals. These colonies must not be confused with the aggregation rosettes of flagellates found among the parasitic Mastigophora. The individuals of aggregation rosettes are capable of immediate separation from the rosette at will. A number of parasitic Flagellata produce non-flagellate stages which are very resistant to external conditions, the assumption of which forms serves to protect the organisms during their transference from one host to another. Such non-flagellate forms possess one or more nuclei, are usually of an oval or rounded contour, and are capable of developing into the full flagellate on the return of more favourable conditions. These forms are often known as the post-flagellate stage of the organism. When ingested by a new host, the post-flagellate coat becomes more flexible, and the phase of the organism which now recommences growth is known as the pre-flagellate stage; it gradually develops into the typical flagellate organism. Many Flagellata live free in fresh and salt water. They prefer stagnant water, rich in organic products of decomposition, such as puddles, swamps and pools. Those forms developing shells and colonies are, as a rule, adherent. A number of species are parasitic in man and animals, living mostly within the intestine or in the blood. It is usual to classify the Flagellata in four orders: _Euflagellata_, _Dinoflagellata_, _Choanoflagellata_, and _Cystoflagellata_, of which only the _Euflagellata_ are of interest to us. This is a group comprising numerous species, for the further classification of which the number and position of the flagella are utilised. The Euflagellata observed in man belong to the Protomonadina as well as to the Polymastigina. The former possess either only one or two similar flagella, or one principal and one or two accessory flagella. The Polymastigina possess at least three flagella of equal size, or four to eight of unequal size, inserted at different points. An undulating membrane may be present in members of both groups. It must also be pointed out that unicellular organisms with one or several flagella are not always classified with flagellates, for such forms occur in Rhizopods as well as temporarily in the lower plants. In addition, the examination of the flagellates, especially the parasitic species, is very difficult on account of their diminutive size and great activity; thus it happens that certain forms cannot with certainty be included in the group because their description is insufficient. Order. *Polymastigina*, Blochmann. The Polymastigina contains flagellates with three to eight flagella. Some of the Flagellata parasitic in man belong to the Polymastigina, and to two or three genera that are easily distinguishable. Genus. *Trichomonas*, Donné, 1837. The body is generally pyriform, the anterior part usually rounded, the posterior part pointed. There are at the anterior extremity three (? four) equally long flagella that are sometimes matted together. A blepharoplast (kinetic nucleus) and basal granule are present, together with a supporting structure known as an axial filament or axostyle. In addition there is an undulating membrane, bordered by a trailing flagellum, that commences at the anterior extremity and proceeds obliquely backwards. The nucleus, which is vesicular, is situated near the anterior extremity, and behind it are one or more vacuoles, none of which seems to be contractile. These flagellates are parasitic in vertebrate animals, and live chiefly in the intestine. *Trichomonas vaginalis*, Donné. The form of the body is very variable, and is elongate, fusiform or pear-shaped, also amœboid. The length varies between 15 µ and 25 µ, and the breadth between 7 µ and 12 µ. The posterior extremity is drawn out to a point and is about half the length of the remainder of the body. The cuticle is very thin and the body substance finely granular. At the anterior extremity there are three--some say four[36]--flagella of equal length which are frequently united together, at least at the base, and are easily detached. [36] To explain this discrepancy it is stated that the border of the undulating membrane can be detached in the form of an independent flagellum. But Parisi (1910) places such quadriflagellate forms in the sub-genus _Tetratrichomonas_, _Arch. f. Protistenk._, xix, p. 232. There is an undulating membrane (fig. 16) which runs spirally across the body, arising from the place of insertion of the flagella, and terminating at the base of the caudal process. A cytostome seldom is recognizable in fresh specimens, but is apparently present. The nucleus is vesicular, elliptical and situated near the anterior extremity.[37] [37] According to Marchand, the nucleus is connected with a line, which becomes visible on addition of acetic acid, terminates at the posterior extremity, and does not correspond to the line of insertion of the undulating membrane. This formation probably is the same as the axostyle in _Trichomonas batrachorum_, Perty. Blochmann (1884) also mentions two longitudinal rows of granules, which commence at the same place as the nucleus and converge posteriorly. Multiplication takes place by division (Marchand). Encysted forms are almost unknown. _Trichomonas vaginalis_ lives in the vaginal mucus of women of various ages, not in normal mucus, but in mucus of acid reaction. It is found in menstruating females as well as in females who have passed the menopause. It occurs in pregnant and non-pregnant women, even in very young girls, provided always that they have a vaginal catarrh with acid reaction of the secretion. Should the acid reaction change, as, for instance, during menstruation, the parasites disappear, as they do likewise on injection of any alkaline fluid into the vagina. A low temperature (below +15° C.) is also fatal to the parasites. These flagellates can pass from the vagina through the urethra into the bladder, and produce severe catarrh, and are not easily removed. [Illustration: FIG. 16.--_Trichomonas vaginalis_, Donné. × 2,000 approx. (After Künstler.) Four flagella are represented, but usually only three are present.] _T. vaginalis_ appeared to be a parasite specific to the female organs and not transmissible to man. However, several observations have since been made that confirm the occurrence of this species in the urethra of the male. The infection apparently takes place through coitus when changes are present in the urethral mucous membrane. At any rate, three cases observed point to this circumstance. Attempts at experimental transmission to rabbits, guinea-pigs and dogs failed (Blochmann, Dock). So far, the manner in which women become infected is unknown. *Trichomonas intestinalis*, R. Leuckart, 1879 = *Trichomonas hominis*, Davaine, 1854. Some authors believe that a second trichomonad inhabiting man, _Trichomonas intestinalis_, R. Lkt., is identical with _Trichomonas vaginalis_, Donné. Leuckart’s species was based on the discoveries of Marchand (1875) and Zunker (1878), who stated that according to all appearances, and in their opinion, it was the same as _Cercomonas intestinalis_, Lambl, 1875 (_nec_ 1859), which they found in the fæces of patients suffering from intestinal disorders. The organism is described by them as being pear-shaped and 10 µ to 15 µ in length and 3 µ to 4 µ in breadth. The posterior extremity terminated in a point (fig. 17). [Illustration: FIG. 17.--_Trichomonas intestinalis_, Lkt. (After Grassi.)] A row of twelve or more cilia was said to commence at the anterior end and extend over the body. Leuckart stated that this parasite, placed by the two authors in the genus _Cercomonas_, was a _Trichomonas_, and that they mistook the undulating membrane for cilia, and overlooked the flagella. Notwithstanding its striking similarity with _T. vaginalis_, it was said to be distinguishable from that species by differences in the undulating membrane. Lambl’s _C. intestinalis_[38] (of 1875) which corresponds with _C. hominis_, Davaine[39] (1854), is regarded by Leuckart as a true Cercomonad (characterized by a flagellum and the absence of an undulating membrane, see p. 61), and is thus generically distinct from _Trichomonas_. [38] Under the term _Cercomonas intestinalis_, Lambl in different years has described two entirely distinct Flagellata, namely, in 1859 (“Mikr. Unters. d. Darm- Excrete,” _Prag. Vierteljahrsschr. f. prakt. Hlkde._, lxi, p. 51; and Lambl, _A. d. Franz-Josephs-Kinderspitale in Prag_, Prag, 1860, i, p. 360), a form that at the present day is termed _Lamblia intestinalis_; and in 1875 (in the _Russian Medical Report_, No. 33), a species identical with _Cercomonas hominis_, Dav. [39] Davaine, C., “Sur les anim. infus. trouv. dans les selles d. malad. atteints du cholera et d’autr. malad.,” _C. R. Soc. Biol._, 1854, ii, p. 129. The correctness of Leuckart’s judgment in regard to Marchand-Zunker’s flagellate was demonstrated by Grassi’s researches, accounts of which were published soon after. In about 100 cases of bowel complaints in North Italy and Sicily, Grassi found Flagellata in the stools, which he first named _Monocercomonas_ and _Cimænomonas_, but later termed _Trichomonas_. However, in opposition to Leuckart, Grassi has also classified Davaine’s _C. hominis_ (= _C. intestinalis_, Lambl, 1875) as _Trichomonas_, and most authors have followed his example. Hence arose the use of the name _Trichomonas hominis_. It was through Janowski (1896) that the former view was again taken up. After a review of the literature, the occurrence of Cercomonads in the intestine of human beings in addition to Trichomonads was considered by the author to have been proved, and he added a description of the Trichomonads. According to this, all morphological distinction between _T. vaginalis_, Donné, and _T. intestinalis_, Leuckart, disappeared. On the other hand, it is worthy of note that the smaller size, the more pear-shaped form, and the longer flagella differentiate _T. intestinalis_ (= _T. hominis_) from _T. vaginalis_.[40] [40] For the present the following should be regarded as synonymous: _Protoryxomyces coprinarius_, Cunningham (_Quart. Journ. Micr. Sci._ (2) 1880, xxi, p. 234), (_Zeitschr. f. Biol._, 1882, viii, p. 251). _Monocercomonas hominis_, Grassi, 1882. _Cimænomonas hominis_, Grassi, 1882. _Trichomonas hominis_, Grassi, 1888. _Cercomonas coli hominis_, May (_Deutsches Archiv. f. klin. med._, 1891, xlix, p. 51). _Monocercomonas hominis_, Epstein (_Prag. med. Wochenschr._ 1893, Nos. 38–40). _Trichomonas confusa_, Stiles (_Zool. Anz._, 1902, xxv, p. 689). _Trichomonas elongata_, _Trichomonas elliptica_, Cohnheim (_Deutsche med. Wochenschr._, 1903, xxix, Nos. 12–14). _Trichomonas elongata_, _Trichomonas caudata_, _Trichomonas flagellata_, Steinberg (_Kiewer Zeitschr. f. neuere Medicin_, 1862). _Trichomonas pulmonalis_, A. Schmidt, (_Münch. med. Wochenschr._, 1895, No. 51), and St. Artault (_Arch. de parasit._ 1898, i, p. 279). The easily deformed pear-shaped body has three free flagella anteriorly, and an undulating membrane with its flagellar border terminating in a short free flagellum posteriorly (figs. 17, 18). The undulating membrane may coil itself spirally round the body. A supporting rod or axostyle projects as a posterior spine. It appears to begin near the nucleus and blepharoplast, which are situated near the more rounded, anterior end of the body. There may be a chromatoid basal supporting line along the body for the undulating membrane. Rows of chromatoid granules are sometimes situated along one side of the axostyle. A cytostome may sometimes be seen. In mice, Wenyon (1907) found these parasites to vary in length from 3 µ to 20 µ. They occur in the cæcum and intestine of mice, where their internal structure seems more obvious than in man. The flagellates divide by longitudinal fission. [Illustration: FIG. 18.--_Trichomonas intestinalis_ from man, showing anterior flagella, cytostomic depression anteriorly, undulating membrane, nuclei, and axostyle. ×2,500. Original.] _T. intestinalis_, R. Leuckart, appears to be capable of settling in all parts of the human intestine in which the contents have an alkaline reaction. Trichomonads have been cited as occurring in the oral cavity by Steinberg, Zunker, Rappin and Prowazek; in the œsophagus by Cohnheim, and in the stomach by Strube, Cohnheim, Zabel, Hensen and Rosenfeld. The normal situation seems to be the small intestine. The parasites then appear in the dejecta, especially in various intestinal diseases the course of which is connected with an increased peristalsis. They are also found in healthy persons, from whom they are obtained after the administration of laxatives. They have been regarded by some workers as commensals, which, however, have the power of accelerating the onset of intestinal complaints, or at least of adding to them. They have been found in cases of carcinoma of the stomach, and in other diseases of that organ in which the acid reaction ceased. Naturally, whether all the reports relate to the same species of Trichomonas must remain undecided. Certain authors (Steinberg, Cohnheim, van Emden) accept several species. Prowazek speaks of a variety of _T. intestinalis_ inhabiting the oral cavity. This was distinguished by a posterior process exceeding the length of the body fourfold, and by a somewhat unusual course of the undulating membrane. The food of this form, which was found in the whitish deposit present, especially in the cavities of carious teeth, consisted almost exclusively of micrococci. Schmidt and St. Artault named the Trichomonads found in pathological products (_e.g._, gangrene, putrid bronchitis, phthisis) of the lungs of man, as _Trichomonas pulmonalis_. Trichomonads have also been found by Wieting in lobular pneumonia in the lungs of pigs. It is still uncertain in what way the infection takes place. Experiments in the transmission of free trichomonads to mammals (_per os_), in which the same or allied species occur (guinea-pigs, rats, apes), have been without result. Probably encystment is necessary. Such conditions are mentioned by May, Künstler, Roos, Schurmayer, van Emden, Prowazek, Galli-Valerio and Schaudinn. According to Prowazek, intestinal trichomonads of rats become encysted for conjugation. In the cyst an accumulation of reserve food material occurs, causing distension. The nuclei of the conjugants each give off a reduction body and, after fusion, produce the nuclei for the daughter individuals. According to Schaudinn the intestinal trichomonads lose their flagella before conjugation, become amœboid and encyst in twos, the formation of a large agglomeration of reserve substance accompanying this. Galli-Valerio found double-contoured cysts in the fæces of trichomonad-infected guinea-pigs, after the fæces had been kept for a month in a damp chamber. When exposed to heat small flagellates escaped from them. Administration of such material containing cysts resulted in severe infection with trichomonads, and death of the experimental guinea-pigs followed. The cyst wall is clearly a protection against the deleterious acid reaction of the stomach contents. Alexeieff (1911) and Brumpt (1912) think that the trichomonad cysts of man are really fungi, while other workers also doubt encystment among trichomonads. Wenyon (1907) states that _T. intestinalis_ in mice produces spherical contracted forms which escape from the body in the fæces. Air, water, and under certain circumstances even food may be regarded as vectors for the trichomonads. The occurrence of the organisms in the oral cavity, and still more so in the lungs, is in favour of the air being the transmitting agent. An observation made by Epstein supports the idea of water transmission. Multiplication of the trichomonads, once they have gained access to the body, is effected by longitudinal division commencing at the anterior end (Künstler). “Cercomonads” with several flagella and an undulating membrane, as well as trichomonads, have been observed by Ross in some cases of cutaneous ulcers. Mello-Leitao (1913)[41] has described flagellate dysentery in children in Rio de Janeiro. He states that it is due to _T. intestinalis_ and _Lamblia intestinalis_ either separately or together. Flagellate dysentery, he thinks, is benign and is the most frequent form of dysentery in infants. The flagellates are pathogenic to infants under three years of age. Escomel (1913)[42] found 152 cases of dysentery in Peru due solely to Trichomonas. Such cases are probably widespread. [41] _Brit. Journ. Children’s Diseases_, x, p. 60. [42] _Bull. Soc. Path. Exot._, vi, p. 120. Genus. *Tetramitus*, Perty, 1852. *Tetramitus mesnili*, Wenyon, 1910. Syn.: _Macrostoma mesnili_, _Chilomastix mesnili_, _Fanapapea intestinalis_. The genus _Tetramitus_ differs from _Trichomonas_ in possessing an undulating membrane inserted in a deep groove or cytostome. There are three anterior flagella. The pear-shaped organism measures 14 µ by 7 µ, but smaller examples occur. _T. mesnili_ occurs in the human intestine, having been described by Wenyon[43] (1910) from a man from the Bahamas in the Seamen’s Hospital, London. Its occurrence is widespread. Alexeieff considers that _Macrostoma_ and _Tetramitus_ are synonymous. The parasite is the same as _Fanapapea intestinalis_, Prowazek, 1911, from Samoa. Brumpt (1912) found _T. mesnili_ to be the causal agent of colitis in a Frenchwoman. Nattan-Larrier (1912) considers it of little pathological importance. [43] _Parasitology_, iii, p. 210. Gäbel[44] (1914) described an interesting case of seasonal diarrhœa acquired in Tunis, in which a new Tetramitid was the causal agent. The organism was pear-shaped, without an undulating membrane, and measured 6·5 µ to 8 µ by 5 µ to 6 µ. The cytostome was large, and there was no skeletal support. Encystment occurred. Gäbel named the organism _Difämus tunensis_ and considered that it was pathogenic. [44] _Arch. f. Protistenk._, xxxiv, p. 1. Genus. *Lamblia*, R. Blanchard, 1888. Syn., _Dimorphus_, Grassi, 1879, _nec_ Haller, 1878; _Megastoma_, Grassi, 1881, _nec_ de Blainville. The body is pear-shaped, with a hollow on the under surface anteriorly. It has four pairs of flagella directed backwards, of which three pairs lie on the borders of the hollow disc, and the fourth arises from the pointed posterior extremity. *Lamblia intestinalis*, Lambl, 1859. Syn.: _Cercomonas intestinalis_, Lambl, 1859 (_nec_ 1875); _Hexamitus duodenalis_, Davaine, 1875; _Dimorphus muris_, Grassi, 1879; _Megastoma entericum_, Grassi, 1881; _Megastoma intestinale_, R. Blanch., 1886; _Lamblia duodenalis_, Stiles, 1902. The organism is pear-shaped and bilaterally symmetrical. It is from 10 µ to 21 µ long and 5 µ to 12 µ broad and possesses a thin cuticle. Anteriorly an oblique depression is present, which functions as a sucking disc (fig. 19, _s_). Its edges are raised above the general surface and are contractile. It corresponds to a peristome and acts as an adhesive organ (fig. 20, _b_, _c_). No true cytostome is present. A double longitudinal ridge, representing axostyles, extends from the sucking disc to the tapering posterior extremity, which is prolonged as two flagella from 9 µ to 14 µ long. _Lamblia intestinalis_ possesses eight flagella (fig. 19). The first pair of flagella, which cross one another, arise in a groove formed by the anterior edge of the sucking disc. Two pairs of flagella (lateral and median) are inserted on the posterior edge of the disc, while the posterior flagella occur at the tapering posterior extremity of the body. Basal granules are found at the bases of the flagella. The median flagella are most active in movement, the anterior and lateral flagella being less motile, as they are partially united to the body for part of their length. The nuclear apparatus is situated in the thin, anterior, hollowed part of the body. It is at first dumb-bell shaped, the “handle” of the dumb-bell being formed by a very slight connecting strand, which eventually separates, so that the flagellate becomes binucleate, and thus completes the general bisymmetry of the organism. There is a karyosome in each nucleus. Other bodies of unknown function, and possibly composed of chromatin, occur on or near the axostyles. [Illustration: FIG. 19.--_Lamblia intestinalis_. A, ventral view; B, side view; N, one of the two nuclei; _ax._, axostyles; _fl_^1, _fl_^2, _fl_^3, _fl_^4, the four pairs of flagella; _s_, sucker-like depressed area on the ventral surface; _x_, bodies of unknown function. (After Wenyon.)] Division has not been observed in the flagellate stages of the Lamblia, but it occurs within the cysts. The resistant cysts (fig. 20, _e_) are oval and are surrounded by a fairly thick, hyaline cyst wall. They measure 10 µ to 15 µ by 7 µ to 9 µ, and may be tetranucleate. According to Schaudinn, the cysts arise from the conjugation of two individuals, and nuclear rearrangement occurs. _L. intestinalis_ occurs in its flagellate stage in the duodenum and jejunum, and rarely as such in the other parts of the intestine. Normally it is found in the large intestine as cysts, which are voided with the fæces. The hosts of Lamblia include _Mus musculus_, _M. rattus_, _M. decumanus_, _M. silvestris_, _Arvicola arvensis_ and _A. amphibius_, the dog and cat, rabbit, sheep and man. Cysts voided with the fæces of infected animals reach plants or drinking water, and thence are transferred to man. The flagellate in these different hosts exhibits some variation in size and in the problematic chromatic bodies. Bensen has suggested the species _L. intestinalis_ from man, _L. muris_ from the mouse and _L. cuniculi_ from the rabbit. It is not certain whether these different species are necessary, as the variation may be due to differences of environment. [Illustration: FIG. 20.--_Lamblia intestinalis._ _a_, from the surface; _b_, from the side; _c_, on intestinal epithelium cells; _d_, dead and _e_, encysted. (After Grassi and Schewiakoff.)] Like Trichomonas, Lamblia can multiply under inflammatory conditions of the alimentary tract. Thus they are found in cases of diarrhœa, carcinoma of the stomach, etc. The parasites attach themselves by their sucking discs to the epithelial cells of the gut (fig. 20, _c_), and though their numbers may be very great, their direct pathological significance is not fully known. Their occurrence in cases of diarrhœa has been explained as being due to the increased peristalsis, which has detached the parasites from the epithelium. Free flagellate forms perish in stools if kept, more especially if the temperature falls below 0° C. or rises above 40° C. Lamblia has often been found in dysenteric diseases, especially in the East, and is said to be the causal agent of certain diarrhœas in India. Mathis (1914)[45] found Lamblia in cases of diarrhœa with dysenteriform stools in Tonkin. He also discovered healthy carriers of Lamblia cysts. [45] _Bull. Soc. Med. Chirurg. Indo-Chine_, v, p. 55. The parasite under discussion was first observed by Lambl (1859) in the mucous evacuations of children. He regarded the parasite as a Cercomonad and termed it _Cercomonas intestinalis_, which name as a rule is applied to _Cercomonas hominis_, Davaine, although Stein had already pointed out the difference between the two species. Grassi (1879) observed this species first in mice (calling it _Dimorphus muris_), and subsequently in human beings in Upper Italy and named it _Megastoma entericum_. Bütschli and Blanchard then laid stress on the identity of this species with Lambl’s _C. intestinalis_ (1859), and consequently called it _Megastoma intestinale_. Later, Blanchard drew attention to the circumstance that the generic name _Megastoma_ chosen by Grassi had already been used four times for various kinds of animals, and established the genus _Lamblia_. Accordingly, _L. intestinalis_ is the valid name, and should be generally adopted. In Upper Italy the parasite in the encysted condition has also been seen by Perroncito in man. At the same time, Grassi and Schewiakoff began a new investigation of specimens from mice and rats. In Germany, _L. intestinalis_ was found by Moritz and Hölzl, Roos, Schuberg and Salomon. Moritz and Hölzl confirmed the relative frequency of the species. In Königsberg, Prussia, a student found encysted _Lamblia_ in his fæces. One case was reported from Finland by Sievers, another case from Scandinavia by Müller. Frshezjesski and Ucke reported cases from Russia. Jaksch announced the occurrence of the parasite in Austria; Piccardi mentioned their presence again in Italy. They were reported from Egypt by Kruse and Pasquale, and from North America (Baltimore) by Stiles. Noc stated that 50 per cent. of the population of Tonkin harboured _Lamblia_. Finally, the structure of _L. intestinalis_ has been described by Metzner (1901), and by Wenyon[46] (1907) in mice. [46] _Arch. f. Protistenkunde_, Suppl. i, p. 169. In all these cases _L. intestinalis_ has been observed in the small intestine, or in the evacuations of patients with intestinal diseases. It has also been found in the intestine of healthy subjects. Just as _Trichomonas intestinalis_ may be found inhabiting the stomach in diseases of that organ, in which an alkaline reaction is present (carcinoma), so has _L. intestinalis_ been found to occur under similar circumstances (Cohnheim, Zabel). However, in Schmidt’s case, 1 per cent. hydrochloric acid was certainly stated to be present. Infection takes place by the ingestion of cysts (fig. 20, _e_), as was established by Grassi, experimentally on himself. Cereal food-stuffs, contaminated with Lamblia cysts from vermin of the locality, such as rats and mice, serve to convey the infection to man. Such cysts may probably be found in street-dust, etc. Stiles induced infection in guinea-pigs, and Perroncito in mice and rabbits, by means of cysts of Lamblia from human beings. Stiles suspected that flies could transport Lamblia cysts. Mathis (1914) found that _L. intestinalis_ was not amenable to emetine, at any rate in its cystic stage. Order. *Protomonadina*, Blochmann. The smallness of the Protomonadines and their less superficial situation than the Polymastigines, may be the cause that so far as the species occurring in man are concerned, they were formerly less well known. As regards parasitic species, this group may be divided as follows, according to the number of flagella and the presence or absence of an undulating membrane:-- (1) _Cercomonadidæ_, with one flagellum at the anterior extremity, without an undulating membrane. (2) _Bodonidæ_, with two flagella, without an undulating membrane, except in Trypanoplasma. (3) _Trypanosomidæ_, with one flagellum, and an undulating membrane along the length of the body in some genera. Family. *Cercomonadidæ*, Kent emend. Bütschli. Small uniflagellate forms, without cytostome. Genus. *Cercomonas*, Dujardin emend. Bütschli. Oval or rounded organisms, with the aflagellar end often drawn out into a tail-like process. *Cercomonas hominis*, Davaine, 1854. Davaine found flagellates in the dejecta of cholera patients. They had pear-shaped bodies, lengthening to a point posteriorly. Their length was from 10 µ to 12 µ, and a flagellum about twice as long as the body projected from one extremity (fig. 21). A nucleus was hardly recognizable. Occasionally a somewhat long structure (cytostome?) appeared at the anterior extremity. The animals moved with remarkable activity. They also attached themselves by means of their posterior extremities and swung about around the point of attachment. Davaine found a smaller variety, only about 8 µ long, in the dejecta of a typhoid patient (fig. 21, _b_). [Illustration: FIG. 21.--_Cercomonas hominis_, Dav. _a_, larger, _b_, smaller variety. Enlarged. (After Davaine.)] [Illustration: FIG. 22.--_Cercomonas hominis_, Dav. From an Echinococcus cyst. (After Lambl.)] The Flagellata observed by Ekeckrantz (1869) in the intestine of man belong to this form--at least to the larger variety--and Tham (1870) reported fresh cases soon after. Lambl’s publication of 1875, which was written in Russian, and became known through Leuckart’s work on parasites, also alludes to apparently typical Cercomonads, which, however, were discovered, not in the intestine, but in an _Echinococcus_ cyst in the liver (fig. 22). The elliptical, fusiform, rarely pear-shaped or cylindrical bodies of the parasites measured 5 µ to 14 µ in length, and were provided with a flagellum at one end, while the other extremity usually terminated in a long point. An oral aperture occurred at the base of the flagellum, and there were one or two vacuoles near the posterior extremity. Longitudinal division was also observed (fig. 22). As already mentioned, this form, which Lambl termed _Cercomonas intestinalis_, differs considerably from the form found by the same author in 1859, which received the same designation (_cf. Lamblia intestinalis_, p. 60), but it corresponds with _Cercomonas hominis_, Davaine. The latter, as well as _C. intestinalis_, Lambl, 1875, is usually classed with the Trichomonads, but, as has already been remarked (_cf._ _Trichomonas intestinalis_, p. 54), this cannot be considered correct, as only _one_ flagellum is present. _Cercomonas vaginalis_ (Castellani and Chalmers, 1909) was found in the vagina of native women in Ceylon. Other species of _Cercomonas_ have, at various times, been recorded from man. However, the parasitic species of the genus _Cercomonas_ require further investigation. According to Janowski (1896–7), typical Cercomonads have also been observed in the intestine of man by Escherich, also by Cahen, Massiutin, Fenoglio, Councilman and Lafleur, Dock, Kruse and Pasquale, Zunker, Quincke and Roos, and others. However, it is an open question whether the Flagellata observed by Roos in one of his cases belonged to Davaine’s species, the size showing some deviation (14 µ to 16 µ). In his, as in many other cases, doubts have been raised as to whether the flagellates found in the stools had actually lived in the intestine, or had subsequently appeared in the fæces: for this a surprisingly short time only is necessary. Salomon also appears to have observed Cercomonads (_Berl. klin. Wochenschr._, 1899, No. 46). As with _T. intestinalis_ so with _C. hominis_, it appears that the parasite settles not only in the intestine but also in the air-passages. This is demonstrated by the statements of Kannenberg and Streng of the occurrence of Monads and Cercomonads in the sputum and putrid expectoration in gangrene of the lungs, which no doubt apply to _C. hominis_ (_cf._ also Artault). Possibly also the Flagellata observed in the pleural exudation by Litten and Roos may be included here; this is the more probable in Roos’s case as the process ensued in the pleura after the breaking through of a vomica. Perroncito and Piccardi have described encysted stages of Cercomonads. *Monas pyophila*, R. Blanch., 1895. [Illustration: FIG. 23.--_Monas pyophila_, R. Blanch. (After Grimm.)] R. Blanchard thus designates a Flagellate that Grimm found in the sputum, as well as in the pus of a pulmonary and hepatic abscess, in the case of a Japanese woman living in Sapporo. The parasites resemble large spermatozoa (fig. 23). The body, 30 µ to 60 µ, has the shape of a heart or a myrtle leaf, and is surrounded by a thick cuticle which is supposed to extend into the interior of the body, dividing it into three parts. A long appendix at the rounded pole is covered for the greater part of its length by the cuticle; the extremity, however, is free and resembles a flagellum. The parasites were very active, frequently changed their shape, and were able to retract the long appendix within the body, which then assumed a round form. [This organism requires further investigation.] Family. *Bodonidæ*, Bütschli. _Protomonadina_ which are either free-living or parasitic, with two dissimilar flagella, while the possession of an undulating membrane and of a kinetic nucleus or blepharoplast is variable. There are three genera:--