10. Caudal extremity.]

The placenta is formed of dilated blood vessels which meet the maternal blood vessels, also dilated, in the uterine wall, allantois later on becomes the umbilical cord. In the placenta the embryonic and maternal vessels without actually communicating, are placed in intimate contact, which allows nutritive matter and oxygen to pass by endosmosis from the maternal vessels to those of the embryo. Figure 21 shows a human embryo at the beginning of the fifth week of pregnancy. [Illustration: FIG. 22. Sagittal section of a primipara in the last month of pregnancy.] =Duration of pregnancy. Birth.= Pregnancy lasts from conjugation, which is synonymous with conception, till birth, that is about nine months (ten lunar months of four weeks). The embryo is then ready to separate from the maternal body (Fig. 22). By the act of birth it is expelled violently, bringing with it the umbilical cord and the placenta (Fig. 23). Immediately afterward the empty womb contracts strongly and gradually recovers its former size. The sudden interruption of its communications with the maternal circulation deprives the embryo, which has suddenly become a child, of its nutritive matter and oxygen. [Illustration: FIG. 23. Sagittal section of frozen body of a woman in labor: the head of the child is engaged in the neck of the womb; the orifice of the neck of the womb (_os uteri_) is already fully dilated and the bag of waters commences to project from the vulva: it is formed by the former membranes of the egg and the decidua.] In order to avoid suffocation it is obliged to breathe atmospheric air immediately, for its blood becomes dark by saturation with carbonic acid, which irritates the respiratory nerve centers. The first independent act of the new-born child is, therefore, a nervous reflex determined by asphyxia, and is performed with the first cry. Soon afterward the infant begins to suck, so as not to die of hunger, while the umbilical cord, having become useless, shrivels up, and the placenta is destroyed (some animals eat it). The new-born infant is only distinguished from the embryo soon after birth by its breathing and crying. We may, therefore, say that infancy, especially early infancy, is only a continuation of embryonic life. The transformations which the infant undergoes from birth to adult age are known to all. They take place more and more slowly, except at the relatively short period of puberty. =Formation of the sexual glands.=--We must remember that at a very early embryonic period certain groups of cells are reserved to form later on the sexual glands. These cells are at first neither male nor female, but are undifferentiated; later on they become differentiated to form in certain individuals, called males, the testicles with their spermatozoa, and in others, called females, the ovaries with their eggs. On this differentiation depends the sex of the individual, and, according as it takes place in one way or the other, all the rest of the body develops with the correlative sexual characters of the corresponding sex (at first the external genital organs peculiar to each sex, then the beard in man, the breasts in woman, etc). =Castration. Correlative sexual characters.=--Castration is the term applied to the extirpation of the sexual glands. When it takes place in infancy it causes a considerable change in the whole subsequent development of the body, especially in man, but also in woman. Man becomes more slender, preserves a high and infantile voice, and his sexual correlative characters develop incompletely or not at all. _Eunuchs_ are men castrated, usually in infancy. To ensure more safety in their harems the Orientals not only remove the testicles but also the penis. Bullocks and horses are bulls and stallions castrated at an early age, and can be distinguished at first sight from normal males. Females who have undergone castration become fat and sometimes take on certain masculine characters. Male human eunuchs have a high-pitched voice, a narrow chest; they remain beardless or nearly so, and have an effeminate character, often intriguing. In both sexes there is a tendency to neurosis and degeneration. It is a mistake to qualify the peculiarities of the male eunuch in the terms of female peculiarities; there is only a relative tendency. The eunuch is no more a woman than a bullock is a cow. The characters of castrated individuals are due only to ablation of the sexual glands themselves--the testicles in man and the ovary in woman; mutilation of other sexual organs, internal or external, such as the penis, womb, etc., produces no result of this kind. It would even appear to result from recent experiments that reimplantation of a sexual gland in any part of the body is sufficient to arrest the production of the special peculiarities of the eunuch. All these facts, almost inexplicable hitherto, become comprehensible by the aid of the engraphia of the mnemic energies. (Vide above; _Semon_). The sexual glands, being of undifferentiated origin, contain the energies of both sexes. The ecphoria of one of them provokes that of its correlative characters and excludes that of the characters of the other. If ecphoria of the sexual glands is arrested by castration before it is finished, this paralyzes the predominance of that of its corresponding correlative characters and reëstablishes a kind of intermediate or undifferentiated equilibrium between the ecphorias of the correlative hereditary sexual characters of the two sexes. On the other hand, if the sexual glands of an adult are removed, his body is not sensibly modified. The sexual functions do not cease completely, although they cannot lead to fecundation. Men castrated in adult age may cohabit with their wives; but the liquid ejaculated is not semen but only secretion from the accessory prostatic gland. Adult women after castration preserve their sexual appetite, and sometimes even their menstruation, for a certain time. They generally become fat and often suffer from nervous troubles and change in character. The ecphoria of the correlative sexual characters being complete in the adult, suppression of the sexual glands can only act on their direct functions. In different species of animals, the correlative sexual characters of which we have spoken vary enormously; sometimes the differences are insignificant, at other times they are considerable; while we can hardly distinguish a male swallow from a female, the cock and hen, the peacock and peahen, the stag and hind are very different from each other. In man, the correlative sexual characters are very distinct, even externally. These characters may extend to all parts of the body, even to the brain and mental faculties. In some of the lower animals, for example the ants, the sexes differ remarkably from each other and appear to belong to different zoölogical families. The eyes, the form of the head, the color, and the whole body differ so much that, when a case of pathological lateral hermaphrodism is produced (that is, when the sexual glands are male on the one side and female on the other), we can exactly determine the male or female character on each portion of the body. We thus see hermaphrodite ants with one half of the body male and the other half female--black on one side and red on the other, a large eye on one side and a small eye on the other, thirteen joints in one antenna and twelve in the other, and so on. In this case the mental faculties are sometimes female, sometimes male, according as the ecphoria of the brain is influenced by the hereditary mneme of the male or female part of the hermaphrodite sexual organs, which results in a male or female brain. I have seen hermaphrodite ants in which two parts of the thorax formed a crossed hermaphrodism; in front, male on the right and female on the left, behind female on the right and male on the left. Further; among ants which live in societies, the progressive transformation of the species, or phylogeny, has produced a third sex derived from the female sex--the worker; sometimes there is even a fourth--the warrior. In these two forms the wings are absent, but the head and brain are much larger; the sexual organs remain female, but are very small. While the large brain (pedunculated bodies of the supra-esophageal ganglion) is almost rudimentary in the male, it is well developed in the female and very large in the worker and the warrior. Among these singular animals exist pathological hermaphrodites, not only between males and females, but between males and workers, and not only lateral but mixed and crossed in all possible ways. I have seen a hermaphrodite, whose abdomen and sexual organs were almost entirely male, accomplish all the complex instinctive actions of a worker of his species (expeditions, attacks on a hostile ant heap, abduction of chrysalids), thanks to its head and brain which were of the worker type. The female itself is incapable of such complex actions. I cite these facts here as material for study, for we are only too prone in this domain to generalize prematurely and to draw too hasty conclusions. In reality, there is still a wide field for study of the greatest interest. There are animals which are normally and physiologically hermaphrodite, for they possess in the normal state male and female sexual glands and fecundate themselves, such as the solitary worms, or in pairs such as the snails. In the latter case there is copulation, during which each animal plays the parts of both male and female. In man and other vertebrates, hermaphrodism is always abnormal. In man it is extremely rare and nearly always very incomplete, being usually limited to the external or correlative characters. =Heredity.=--It results from what we have said that every living being reproduces, more or less identically, in its specific characters, the whole life of its parents and less remote ancestors, and constitutes the continuation of life from a minute part of their bodies. Each individual life thus repeats an entire cycle of development called _ontogeny_, which is peculiar to all individuals of the species. Here we must mention three fundamental points: (1). In its principal characters, each individual is the copy of its parents or direct ancestors, with correlative sexual peculiarities which we have mentioned, and with individual variations due to the combinations of varieties by conjugation, and the alternating or unequal ecphorias of hereditary characters; that is to say paternal or maternal hereditary engrams. (2). No individual is absolutely identical with another. (3). On the average, each individual resembles more especially its direct ancestry and its parents, and differs more markedly from its parentage the more this is remote. We shall see later on that the ancestral relationship of the different groups, species and varieties of animals has been fairly well fixed, and we may say that the third of the laws stated above is equally true in a wider sense. In fact the species and varieties of animals which are near related resemble each other, while the _genera_, families and classes are more dissimilar as their relationship is more remote. We employ here the terms resemblance, homology and difference in their profound and general sense. Certain purely external resemblances, due to phenomena of convergence, must not be considered as homologies in the sense of hereditary relationship. Thus, in the language of natural history we do not say that a bat resembles a bird, nor that a whale resembles a fish, for here the resemblances are due simply to aërial or aquatic life which produces the effects of convergence, while the internal structure shows them to be quite dissimilar organisms. Although it swims in the sea the whale is a mammal; its fins at first sight resemble those of a fish, but they are really the homologues of the four limbs of other mammals and contain the corresponding bones. In man, we see that brothers and sisters resemble each other in a general way, but that each one is dissimilar in some respects from the others. If we compare different families with many children we find that brothers and sisters resemble each other the more their parents are alike and come from a uniform ancestry which has undergone little crossing, while the crossing of different races and human varieties results in the production of individuals which differ from each other considerably, even when they come from the same couple. If we examine things more closely, we find that the characters of each of the offspring of the same couple present neither simple repetition nor an equal mixture of the peculiarities of the parents, but very diverse combinations of the characters of several ancestors. For instance, children may bear a striking resemblance to a paternal grandfather, a maternal grand-aunt, or a maternal great-grandmother, etc. This is called _atavism_. Some children resemble their father, others their mother, and others a kind of mixture of father and mother. A closer examination reveals further very curious facts. An infant which, in its early years, strongly resembles its father, may later on resemble its mother, or inversely. Certain peculiarities of a certain ancestor appear suddenly, often at an advanced age. It is needless to say that peculiarities concerning the beard cannot appear till this has grown, and this simple fact is so characteristic that it has been called _hereditary disposition_. Everything may be transmitted by heredity, even to the finest shades of sentiment, intelligence and will, even to the most insignificant details of the nails, the form of the bones, etc. But the combinations of ancestral qualities vary so infinitely that it is extremely difficult to recognize them. Hereditary dispositions arise from the energy of two conjugated germs during the whole of life and till death. Old people sometimes develop peculiarities hitherto unknown in them, owing to the fact that one or more of their ancestors also presented the same phenomena at an advanced age. _Semon_ has clearly proved that, although forming an infinite number of combinations the engrams or hereditary energies never blend in the proper sense of the term, and in the light of his exposition the above facts are more clearly explained than they had been hitherto. The experiments of _Mendel_ have shown in plants a certain alteration in the hereditary ecphorias of the products of dissimilar parents. Certain parental characters, according as they are added or subtracted, may disappear during one or two generations, to reappear all the more strongly in the following generations. In short, there are a number of phenomena, the laws of which may be more clearly explained to us in the future. To sum up, each individual inherits on the average as much from his paternal as from his maternal side, although the minute nucleus of the spermatozoid is the only agent concerned on the paternal side, while the mother provides not only the egg which is much larger, but also nutrition during the nine months of embryonic life. We can only conclude that in the egg also it is only from the part of the nucleus which conjugates with the male nucleus that arise all the inherited maternal peculiarities; that all the rest is only utilized as food; and that the nutritive blood of the mother in no way influences the inherited energies of the offspring. This shows the capital importance of conjugation and of the substance of the conjugated nuclei, especially of their chromatin. The fact that, in certain of the lower animals, the protoplasm of the egg without nuclei may occasionally produce some phenomena of cell division, thanks to its inherited mnemic engrams, in no way alters the fundamental principle which alone occurs in man, for this vicarious action, which is moreover rudimentary, only happens when the protoplasm of the egg is not consumed by the conjugated nuclei. Parthenogenesis is also a very interesting phenomenon in the history of our animal ancestors, but for the same reasons it has no direct interest for humanity. If we take into consideration all the observations of which we have just spoken, which are as simple as they are irrefutably demonstrated, it is hardly possible to interpret them in any other way than by the following hypothesis: In each sexual gland, male or female, the germinal cells which are produced by division of the cells of the embryo, reserved primarily for reproduction, differ considerably from each other in quality and contain in their infinitely small atoms very diverse and irregularly distributed energies, inherited from their different ancestors. Some contain more paternal and others more maternal energy, and among the former there are some contain, for example, more paternal grandfather and others more maternal grandmother, and so on to infinity, till it is impossible to discover the ancestral origin of the fully grown individual we are examining. The same holds good for the energies of the maternal cells. At the time of conjugation, the qualities of the child which will result from it depend therefore on conditions of the ancestral qualities of the conjugated egg and spermatozoön. Moreover, although of the same size, the nuclei which become conjugated are evidently of unequal strength; the energies of one or the other predominate later on in the embryo, and still later in man. According to circumstances the latter will resemble more or less his paternal or maternal progenitors. Moreover, the different organs of the body may receive their energies from different parts of the conjugated nuclei in different degrees. A person may have his father's nose and his mother's eyes, the paternal grandmother's humor and the maternal grandfather's intelligence, and all this with infinite degrees and variations, for it is only a matter of more or less accentuated averages. In my own face the two halves are distinctly different, one resembling my maternal ancestry and the other, in a lesser degree, my paternal ancestry, these points being seen distinctly in photographs taken in profile. Each germinal cell contains the hereditary mneme of its ancestors, paternal and maternal, and the two cells united by conjugation (Fig. 17) that of the ancestors of each of them. We have spoken above of ecphorias produced according to _Mendel's_ law and reproducing characters which have been latent during one or two generations. Darwin was the first to study this interesting fact, which shows how atavism often results from the crossing of varieties. There are several varieties of fowls which do not brood; if two of these varieties, B and C, are crossed excellent brooders are obtained. _Semon_ assumes that in each of the non-brooding varieties the ancestral energy, A, of the primary species, is weaker than that of varieties B and C; we have then A > B, and A < C. But if B is coupled with A the product represents the value B + C + A + A. Then B and C are in equilibrium; and A being doubled becomes stronger than each of them and arrives at ecphoria in their place, which restores the faculty of brooding to the product of crossing. _De Vries_ has shown, in the crossing of varieties with their primary species, more or less analogous phenomena which he calls "Vicino-variations." Conjugation leads to infinite combinations and variations which the law of heredity traverses like a guiding line. The celebrated zoölogist, _Weismann_, considers that the chromatin of each germinal cell contains a considerable quantity of particles each of which is capable of forming an entire organism similar to the parents; these he calls "ides." According to _Weismann_, each ide is subdivided into "determinants" from which each part of the body is derived, being potentially predetermined in them. According to the action of a yet unknown irritation male or female determinants develop in each individual of the animal species with separate sexes. But if the determinants are disordered, either by abnormal variations or by pathological causes, hermaphrodites or monstrosities may be produced. In animals which are normally hermaphrodite (snails, etc.), there is only one kind of sexual determinant, while in polymorphous animals (ants, etc.), there are as many as the polymorphous forms. The conception of "ides" and "determinants" is only a hypothesis to which we must not attach much value. The mnemic laws established by _Semon_ give a much better explanation of the facts. It has often been maintained that the qualities of higher forms of man are exhausted in a few generations, while the mass of mediocrities continually produce new genius. The fact that the descendants of distinguished men are often mediocre and that remarkable men suddenly arise from the common people, appears at first sight to support this superficial assertion. It is forgotten, however, that in a people whose average mass consists of thousands or millions of individuals, while men of higher powers are only counted by units or dozens, all this arithmetic is reduced to absurdity by the inequality of numbers, as soon as the law of heredity is understood. To make a more exact calculation, it would be necessary to compare the number of superior men who have arisen from some hundreds of the most distinguished families of a country with that of distinguished men who have arisen from some millions of the rest of the people, and then calculate the percentage. It is also necessary to take into account the means employed in the education of the individuals. If education is obligatory and gratuitous in a country, this factor will have less importance. Another error which is committed in such cases is to neglect the influence of the maternal lineage. A common woman will lower the level of the offspring of a distinguished husband, and inversely. In his "History of Science and Scientists" _Alphonse de Candolle_ has given irrefutable proof that the posterity of high-class men furnishes a great number proportionally of men high class in their turn, compared with that of the average population. This shows the value of the usual twaddle concerning this question. It is inconceivable that the laws of heredity should make an exception of the mental qualities of man. Moreover, the most deceptive point is the contrast of a man of genius with his children, who do not rise to his standard because they represent a combination of his ancestral energies with those of their mother. This contrast makes the children appear unfavorably, while the public has a general tendency to exaggerate the value of a great man. The theory of the mneme throws light on this subject, by introducing a new factor in the question, that of ecphoria of the cerebral engrams of the ancestors, accumulated in the hereditary mneme. =Heredity of Acquired Characters.=--While _Darwin_ and _Haeckel_ affirmed the possibility of the heredity of characters acquired during life by different tissues, for instance the brain, _Weismann_ limits the possibility to everything that can modify the nucleoplasm of the germinal cells. We must first eliminate the question of the phenomena of blastophthoria, which we shall consider next, and which _Weismann_ was, I think, the first to comprehend, without giving them the name. On one hand we see the singular effects of castration, which we have already considered; on the other hand, an extraordinary constancy in the hereditary characters of the species. For more than three thousand six hundred years, which corresponds to about eight hundred generations, the Jews have been circumcised. Nevertheless, if a Jew ceases to circumcise his offspring the prepuce of his children grows as it did three thousand six hundred years ago, although, during the eight hundred generations in question, its absence from birth has prevented it reacting on the germinal cells of the individuals. If the engraphia of the external world could sensibly modify in a few generations the hereditary mneme of the species, it appears evident that the Jewish infants of the present day would be born without prepuce, or at least with an atrophied one. It is on such facts, which are innumerable in natural history, that _Weismann_ relies to repudiate absolutely the heredity of characters acquired by non-germinal organs and to attribute the development of organisms to blends and combinations due to conjugation, or crossing, as well as to natural selection, which he regards as all-powerful. _Darwin_ well recognized the difficulty in question, and being unable to explain the facts, had recourse to the hypothesis of _pangenesis_, that is of small particles detached from all parts of the body and transported by the blood to the germinal cells, to transmit to them, for example, the qualities acquired by the brain during life. This hypothesis was so improbable that _Darwin_ himself was forced to recognize it. Let us examine the facts. On the one hand a newly born Chinese transported and brought up in France will learn French, and will show no inclination to learn or understand Chinese. This well-established fact seems in favor of _Weismann_ and against the heredity of acquired characters. But, on the other hand, we cannot understand how the evolution of the brain and its functions takes place, without admitting that in one way or another the characters acquired by habits repeated during many generations gradually accumulate in the form of hereditary dispositions in the germinal protoplasm. It is certain that our brain has progressed since the time when our ancestors were similar to the gorilla, or even the cave man at the beginning of the quaternary age. How can this cerebral progression be explained only by selection which can only eliminate, and by crossings which by themselves can hardly raise the average? It is here that the intervention of an unknown power is necessary, something unexplained, the action of which has been lately recorded in the phenomena of mutations of _de Vries_. _De Vries_ proves that certain variations appear suddenly and without any known cause, and have a much greater tendency to be preserved than the variations obtained by crossing and selection. In my opinion the phenomena of the mneme revealed by _Hering_ and _Semon_ explain the apparent contradictions which have hitherto impaired the theories of heredity. Mnemic engraphy explains, by its infinitesimal and repeated action through numerous generations, how the external world may little by little transmit to the germinal cells the characters which it impresses on organisms. The eight hundred generations during which the prepuce of the Jews has been cut off have not yet sufficed for the ecphoria of the corresponding negative mnemic engraphia; while conjugation and selection modify rapidly and strongly in a few generations; a fact which is more striking and allows of direct experiment. Moreover, a positive engraphia must necessarily act more powerfully, and it seems to me that mutations must be the ecphoria of accumulated former latent engraphias. _Merrifield_ and _Standfuss_, by exposing caterpillars and chrysalids for varying periods to considerable degrees of cold and heat, have determined permanent changes in the specific characters of the butterflies which have emerged from them. _Standfuss_ and _Fischer_ have also shown that, after several generations, by continuing the action of cold on the caterpillars, the variations thus produced can be preserved even after the cold has ceased to act. No doubt the cold acts on the germinal cells as on the rest of the body, but the heredity of an acquired character is thus demonstrated. The experiments of _Miss de Chauvin_ on salamanders (_Axolotl_) are still more conclusive, for we are dealing here with characters acquired through aquatic or aërial media, which can hardly act on the sexual glands. We cannot continue this subject any further and we return to the work of _Semon_. It is needless to say that the nature of mnemic engraphia remains itself an unknown quantity. As long as we are unable to transform inert matter into a living organism we shall remain in ignorance. But, when it is accepted with the laws of the phenomena which it produces, this unknown quantity, as _Semon_ has shown, alone suffices to explain all the rest, and is already a great step toward the comprehension of the laws which govern life. =Blastophthoria.=--By blastophthoria, or deterioration of the germ, I mean what might also be called false heredity, that is to say, the results of all direct pathogenic or disturbing action, especially that of certain intoxications, on the germinal cells, whose hereditary determinants are thus changed. Blastophthoria thus acts on germs not yet conjugated, through the medium of their bearers, and creates at their origin _hereditary stigmata_ of all kinds, while true heredity only combines and reproduces the ancestral energies. Blastophthoria deranges the mneme or hereditary engrams, and consequently a more or less considerable part of their ecphorias during the life of the individuals which arise from them. It is not a question here of the reproduction of the hereditary ancestral energies in the descendants (in different combinations) as is the case in the heredity which we have just studied, but, on the contrary, a question of their perturbation. However, the store of cells reserved as germinal cells in the embryo, the germ of which has been damaged by blastophthoric action, being usually also affected by the disturbing cause, it follows that the pathological change introduced by blastophthoria in the hereditary mneme is transmitted to the descendants by ordinary heredity. In this way blastophthoria deposits the first germ of most pathological degenerations by causing immediate deviation of all the determinants of the germ in the same direction. The most typical and the commonest example of blastophthoria is that of alcoholic intoxication. The spermatozoa of alcoholics suffer like the other tissues from the toxic action of alcohol on the protoplasm. The result of this intoxication of the germs may be that the children resulting from their conjugation become idiots, epileptics, dwarfs or feeble minded. Thus it is not alcoholism or the craving for drink which is inherited. No doubt the peculiarity of badly supporting alcohol is inherited by ordinary heredity as a hereditary disposition, but it is not this which produces the alcoholic degenerations of the race. These are the result of the single blastophthoria. When, on the other hand, a man is found to be imbecile or epileptic as the result of the insobriety of his father, he preserves the tendency to transmit his mental weakness or his epilepsy to his descendants, even when he abstains completely from alcoholic drinks. In fact, the chromosomes of the spermatozoid, from which about a half of his organism has issued, have preserved the pathological derangement produced by the parental alcoholism in their hereditary mneme, and have transmitted it to the store of germinal cells of the feeble minded or the epileptic, who in his turn transmits it to his descendants. From _Weismann's_ point of view his hereditary determinants remain pathologically deviated. All intoxications which alter the protoplasm of the germinal cells may produce blastophthoric degenerations, which continue to menace several successive generations in the form of hereditary taints. Other deviations in the development of the germs may act in an analogous manner to blastophthoria. We have mentioned above the experiments of _Merrifield_ and _Standfuss_ on the caterpillars of certain butterflies. Without being really of a pathological nature, these actions of a physical agent on the hereditary energies resemble blastophthoria. Mechanical action on the embryo may also give rise to pathological products or even mutilation. Thus, _Weismann_ demonstrated the production of degenerate individuals in ants when certain coleoptera were introduced in their nest, the ants being fond of the secretion of the large glandular hairs of the coleoptera. The exact cause of the degeneration has not yet been found, but the fact is certain. In man, certain constitutional affections and congenital anomalies are the result of certain diseases in the procreators, which have affected the germinal cells or the embryo (for instance syphilis). As soon as the blastophthoric actions cease in the procreators, those of their descendants who live under a normal regimen have evidently a tendency to eliminate the blastophthoric organs at the end of several generations and to regenerate themselves little by little. Thanks to the power of the ancestral mneme which tends to reëstablish homophony. However, the data on this subject are insufficient. In this case homophony is represented by the normal equilibrium of the different typical or normal characters of the species. FOOTNOTES: [1] I insert here some passages intended for more advanced readers, but this does not imply that they are of less importance. On the contrary I strongly advise all my readers to try and understand the theories of _Hering_ and _Semon_, which appear to me to throw a new light on the question of transformation and heredity.