CHAPTER XXXI.

OF THE POISONOUS GASES. The subject of the poisonous gases is one of great importance in relation to medical police, as well as medical jurisprudence. They are objects of interest to the medical jurist, because their effects may be mistaken for those of criminal violence, and because they have even been resorted to for committing suicide. They are interesting as a topic of medical police, since some trades expose the workmen to their influence. It has hitherto been chiefly on the continent that use has been made of the deleterious gases for the purpose of self-destruction. Osiander mentions, that Lebrun, a famous player on the horn, suffocated himself at Paris in 1809 with the fumes of sulphur; and that an apothecary at Pyrmont killed himself by going into the _Grotto del Cane_ there, which, like that near Naples, is filled with carbonic acid gas.[2002] Many instances have lately occurred in France of suicide caused by the emanations from burning charcoal in a close chamber. But these poisons come under the notice of the medical jurist chiefly because their effects may be mistaken for those of other kinds of violent death. Several mistakes of this nature are on record. Zacchias mentions the case of a man, who was found dead in prison under circumstances which led to the suspicion, that he had been privately strangled by the governor. But Zacchias proved this to be impossible, and ascribed death to the fumes from a choffer of burning charcoal left in the room.[2003] A more striking instance of the kind occurred a few years ago at London. A woman, who inhabited a room with other five people, alarmed the neighbours one morning with the intelligence that all her fellow-lodgers were dead. On entering the room they found two men and two women actually dead, and another man quite insensible and apparently dying. This man, however, recovered; and as it was said that he was too intimate with the woman who gave the alarm, a report was spread that she had poisoned the rest, to get rid of the man’s wife, one of the sufferers. She was accordingly put in prison, various articles in the house were carefully analysed for poison, and an account of the supposed barbarous murder was hawked about the streets. At last the man who recovered remembered having put a choffer of coals between the two beds, which held the whole six people; and the chamber having no vent, they had thus been all suffocated.[2004]—The following is a similar accident not less remarkable in its circumstances. Four people in _Gerolzhofen_ in Bavaria, were found one morning in bed, some dead, others comatose; and only one recovered. A neighbour who had supped with them, but slept at home, did not suffer. The stomach and intestines were found very red and black; and the coats of the stomach brittle. The contents of the stomach, the remains of their supper, and the wine were analysed without any suspicious substance being found. A little smoke having been noticed in the room by those who first entered it, the stove and fuel were examined, but without furnishing any insight into the cause of the accident. At last the cellar was examined, and then it was found that one of the sufferers had heated a copper vessel there so incautiously, that the fire communicated with the unplastered planks of the floor above. The planks had burnt with a low smothered flame, and the vapours passed through the crevices in the floor.[2005] _What Irrespirable Gases are Poisonous?_ Some gases act negatively on the animal system by preventing the access of respirable air to the lungs; others are positively poisonous. The first point, therefore, is to ascertain which are negatively, and which positively hurtful. M. Nysten, who has made the most connected train of experiments on this subject, conceived that a gas will not act through any other channel besides the lungs, if it exerts merely a negative action:—and that, on the contrary, it certainly possesses a direct and positive power, if it has nearly the same effects, in whatever way it is introduced into the body.[2006] He therefore thought the best way to ascertain the action of the gases would be, to inject them into the blood,—conceiving that, after allowance is made for the mere mechanical effects of an aëriform body, the phenomena would point out the true operation of each. His first object then was to learn what phenomena are caused by the mechanical action of atmospheric air. He found that four cubic inches and a half, injected into the jugular vein of a dog, killed it immediately amidst tetanic convulsions, by distending the heart with frothy blood;—that a larger quantity introduced, gradually caused more lingering death, with symptoms of oppressed breathing, which arose from gorging of the lungs with frothy blood;—and that a small quantity, injected into the carotid artery towards the brain, occasioned speedy death by apoplexy, which arose from the brain being deprived by means of the air of a due supply of its proper stimulus, the blood. Numerous experimental inquiries have been since made on this subject, the latest of which, those of Dr. Cormack, coincide with the first results of Nysten, that air injected into the veins causes death by arrestment of the action of the heart.[2007] Proceeding with these data, Nysten found that _oxygen_ and _azote_ had the same effect when apart, as when united in the form of atmospheric air; that _carburetted hydrogen_, _hydrogen_, _carbonic oxide_, and _phosphuretted hydrogen_ likewise seemed to act in the same way; and that the _nitrous oxide_, or intoxicating gas, although it does not cause so much mechanical injury as the others, on account of its superior solubility in the blood, has the same effect when injected in sufficient quantity, and produces little or none of the symptoms of intoxication excited by it in man.[2008] As to _carbonic acid gas_, he found that, on account of its great solubility in the blood, it is difficult to produce mechanical injury with it; that sixty-four cubic inches are absorbed, and do not excite any particular symptoms; but that when injected into the carotid artery, it occasions death by apoplexy, although it is rapidly absorbed by the blood.[2009] The other gases he tried were hydrosulphuric acid, nitric oxide, ammonia and chlorine; and all of these proved to be positively and highly deleterious. Two or three cubic inches of _hydrosulphuric acid gas_ caused tetanus and immediate death, when injected into the veins, although the gas was at once absorbed by the blood. The same quantity acted with almost equal rapidity when injected into the cavity of the chest. Similar results were obtained when it was injected into the cellular tissue, or even when it was left for some time in contact with the sound skin.[2010] The last important fact has been since confirmed by Lebküchner in his Thesis on the permeability of the tissues;[2011] and it had previously been observed also by the late Professor Chaussier, whose experiments will be mentioned presently (p. 617). In none of Nysten’s experiments with this gas was the blood changed in appearance. _Nitric oxide gas_, according to Nysten, is the most energetic of all the poisonous gases. A very small quantity causes death by tetanus, when introduced into a vein, the cavity of the chest, or the cellular tissue; and it always changes the state of the blood, giving it a chocolate-brown colour, and preventing its coagulation. In one of Nysten’s experiments a cubic inch and three-quarters injected into the chest killed a little dog in 45 minutes.[2012] Dr. John Davy appears to have found this gas not so active.[2013] Nysten found the two other gases, _ammonia_ and _chlorine_, to be acrid in their action. When injected into the veins they kill by over-stimulating the heart; and when injected into the cavity of the chest, they excite inflammation in the lining membrane.[2014] Hébréart farther remarked in his experiments relative to the action of irritants on the windpipe, that chlorine when inspired, produces violent inflammation in the windpipe and its great branches, ending in the secretion of a pseudo-membrane like that of croup;[2015] and that a very small quantity of ammonia has the same effect. From this abstract of Nysten’s researches, it appears to follow, that ammonia and chlorine are irritants; hydrosulphuric acid and nitric oxide, narcotics; oxygen, azote, hydrogen, carburetted hydrogen, phosphuretted hydrogen, carbonic oxide, and nitrous oxide, negative poisons; and carbonic acid, doubtful in its nature. Some of these conclusions do not correspond with the effects observed in man; which will presently be found to lead to the inference, that not only carbonic acid, but likewise carbonic oxide, nitrous oxide, and carburetted hydrogen are narcotics. The reason Nysten did not find these gases injurious was probably, that, before they could pass from the vein into which they were injected, to the brain on which they act, they were in a great measure exhaled from the lungs. The experiments of physiologists since Nysten’s time likewise tend to show that oxygen gas is a positive poison when pure, and that even hydrogen possesses active properties. The inquiries of Mr. Broughton led him to consider hydrogen a positive poison, because animals die in it in half a minute, and the heart immediately after death is found to have lost its contractility. Previous experimentalists had also remarked hypnotic effects from the inhalation of it diluted with oxygen.[2016] As to oxygen, the same physiologist ascertained that when pure, it is a narcotic poison, though a feeble one, as at least five hours of continuous respiration in the pure gas are required to prove fatal.[2017] _Of the Effects of the Poisonous Gases on Man._ According to the effects of the poisonous gases on man, they may be arranged in two groups, the first including the _irritants_, the second the _narcotics_. It might have been therefore a more philosophical mode of arrangement, if the former had been considered under the irritant class of poisons; but it is more convenient to examine the whole deleterious gases together. The _irritant gases_ are nitric oxide gas and nitrous acid vapour, hydrochloric acid gas, chlorine, ammonia, sulphurous acid, and some others of little consequence. _Of Nitric oxide gas and Nitrous acid vapour._—Before nitric oxide gas can be breathed in ordinary circumstances, it is transformed by the oxygen of the air into nitrous acid vapour, of a ruddy colour and irritating odour. Hébréart found that in animals killed by inhaling it the windpipe was much inflamed.[2018] Sir H. Davy tried to inhale it, and with this view took the precaution of previously breathing the nitrous oxide or intoxicating gas, in order to expel the atmospheric air as much as possible from his lungs. But he found that the small quantity of nitrous acid fumes formed with the remaining air was sufficient to cause a sense of burning in the throat, and at once stimulated the glottis to contract, so that none of the nitric oxide gas could pass into the larynx. The subsequent entrance of the external air into the mouth, which Sir Humphrey unluckily had not provided for, was of course attended by the immediate formation of more acid fumes, by which his tongue, cheeks, and gums, were irritated and inflamed; and there is no doubt, as Sir Humphrey himself remarks, that if he had succeeded in inhaling the nitric oxide gas, the same chemical change would have happened in the lungs and excited pneumonia.[2019] The following cases will prove that nitrous acid vapour, disengaged from the fuming nitrous acid, is a very violent and dangerous poison when inhaled. A chemical manufacturer, in endeavouring to remove from his store-room a hamper in which some bottles of nitrous acid had burst, breathed the fumes for some time, and was seized in four hours with symptoms of inflammation in the throat and stomach. At night the urine was suppressed; the skin then became blue; at last he was seized with hiccup, acute pain in the diaphragm, convulsions, and delirium; and he died twenty-seven hours after the accident.[2020] Another case has been described in the Bulletins of the Medical Society of Emulation. It proved fatal in two days, and the symptoms were those of violent pneumonia. In this instance there was pneumonia of one side, and pleurisy of the other; the uvula and throat were gangrenous, and the windpipe and air-tubes dark-red; the veins throughout the whole body were much congested, the skin very livid in many places, and the blood fluid in the heart, but coagulated in the vessels.[2021] Dr. Reitz, a writer in Henke’s Journal, met with two cases of death from the same cause in hatters. They had incautiously exposed themselves too much to the fumes, which are disengaged during the preparation of nitrate of mercury for the operation of felting, and which are well known to be nitric oxide gas converted into nitrous acid vapour by contact with the air. Two men died of inflammation of the lungs excited in that manner; and a third, a boy of fourteen, after sleeping all night in an apartment where the mixture was effervescing, was attacked in the morning with yellowness of the skin, giddiness, and colic, which ended fatally in six days.[2022] _Of Poisoning with Chlorine._—The experiments of Nysten and Hébréart with chlorine, and its well-known irritating effects when inhaled in the minutest quantities, show that it will produce inflammation of the lungs and air-passages. The following is the only instance of poisoning with it in man which has come under my notice. A young man, after breathing diluted chlorine as an experiment, was instantly seized with violent irritation in the epiglottis, windpipe, and bronchial branches, cough, tightness, and sense of pressure in the chest, inability to swallow, great difficulty in breathing or articulating, discharge of mucus from the mouth and nostrils, severe sneezing, swelling of the face, and protrusion of the eyes. Ammonia was of no use; but singular relief was obtained from the inhalation of a little sulphuretted hydrogen, so that in an hour and a half he was tolerably well.[2023] Although this gas is very irritating to an unaccustomed person, yet by the force of habit one may breathe with impunity an atmosphere much loaded with it. I have been told by a chemical manufacturer at Belfast, that his men can work in an atmosphere of chlorine, where he himself could not remain above a few minutes. The chief consequences of habitual exposure are acidity and other stomach complaints, which the men generally correct by taking chalk. He has likewise observed that they never become corpulent, and that corpulent men who become workmen are soon reduced to an ordinary size. It is not probable, however, that the trade is an unhealthy one; for several of this gentleman’s workmen have lived to an advanced age; one man, who died not long ago at the age of eighty, had been forty years in the manufactory; and I have seen in Mr. Tenant’s manufactory at Glasgow a healthy-looking man who had been also about forty years a workman there. It is an interesting fact, that during the epidemic fever which raged over Ireland from 1816 to 1819, the people at the manufactory at Belfast were exempt from it. _Of Poisoning with Ammonia._—For an account of the effects of _ammonia_, which, when in the state of gas, acts violently as an irritant on the mouth, windpipe, and lungs, the reader is referred to the chapter on ammonia and its salts in page 193. It appears to form one of the gases disengaged from the soil of necessaries, as will be noticed presently, and excites inflammation in the eyes of workmen who are incautiously exposed to it.[2024] _Of Poisoning with Hydrochloric Acid Gas._—I have not met with any account of the effects of _hydrochloric acid gas_ on man. But no doubt can be entertained that it will likewise act as a violent and pure irritant. It is exceedingly hurtful to vegetable life. In the course of some experiments performed in 1827 by Dr. Turner and myself on the effects of various gases on plants, we found that a tenth of a cubic inch diluted with 20,000 times its volume of air, so as to be quite imperceptible to the nostrils, shrivelled and killed all the leaves of various plants, which were exposed to it for twenty-four hours.[2025] These experiments were repeated in 1832 by Messrs. Rogerson, apparently in ignorance of them. Their results are on the whole the same; and the slighter effect obtained by them from minute proportions of the gas was evidently owing to the small size of their glass-jars not allowing them to use a sufficient quantity of it.[2026] They farther found that proportions of hydrochloric acid gas, amounting to a twentieth of the air, kill small animals in half an hour with symptoms of obstructed respiration. Their experiments with less proportions are not precise, yet warrant the inference that even a thousandth part of the gas will probably prove fatal in no long time.[2027] _Of Poisoning with Hydrosulphuric Acid Gas._—The _narcotic gases_ are of much greater importance than the irritants, on account of the singularity of their effects, and the greater frequency of accidents with them. This group includes hydrosulphuric acid, carburetted-hydrogen, carbonic acid, carbonic oxide, nitrous oxide, cyanogen, and oxygen. Hydrosulphuric acid gas is probably the most deleterious of all the gases. According to Thenard and Dupuytren, air containing only an 800th of it will kill small birds in a few seconds; and a 290th is sufficient to kill a dog; which, however, will sustain so much as a 400th.[2028] Chaussier previously found, that a horse was killed by breathing atmospheric air which contained a 250th of hydrosulphuric acid gas; and that it acts with energy on animals, whether it be inhaled, or injected into the stomach, anus, or cellular tissue, or even simply applied to the skin. Nine quarts of the gas injected into the anus of a horse killed it in one minute; and a rabbit, whose skin alone was exposed to it, died in ten minutes.[2029] Ulterior inquiries by MM. Parent-Duchâtelet and Gaultier de Claubry,—scarcely so precise however as those of their predecessors,—appear to lead to the conclusion, that its energy is in some circumstances not so great. While superintending the clearing out of some of the choked drains of Paris, they found that the workmen suffered no harm, though they habitually breathed an atmosphere containing from 25 to 80 ten-thousandths of hydrosulphuric acid gas, and on some occasions even so much as one per cent.; nay, on one occasion Gaultier remained several minutes without injury, collecting air for chemical analysis in an atmosphere, which proved to be loaded with three per cent. of the gas.[2030] None of these researches point out the precise manner of death. Dr. Percy of Nottingham informs me he found in 1839, that dogs, which breathed air, containing this gas, quickly died in convulsions like those caused by hydrocyanic acid; that in some instances the heart’s action was observed to have ceased, when the body was opened immediately after death; but that in general it either continued to beat for some time, or could be made to do so when its state of congestion was relieved by withdrawing a little blood. Dr. Turner and I found that hydrosulphuric acid gas is very injurious to vegetables, and that it acts differently from muriatic acid gas, as it appeared to exhaust the vitality of plants and to cause in them a state analogous to narcotic poisoning in animals. Four cubic inches and a half, diluted with eighty volumes of air, caused drooping of the leaves of a mignonette plant in twenty-four hours; and the plant, though then removed into the open air, continued to droop till it bent over altogether and died.[2031] The best description of the effects of this gas on man has been given by M. Hallé,[2032] in his account of the nature and effects of the exhalations from the pits of the Parisian necessaries; which exhalations appear, from the experiments of Thenard and Dupuytren, to be mixtures chiefly of ammonia and sulphuretted-hydrogen. The symptoms, in cases where the vapours are breathed in a state of concentration, are sudden weakness and all the signs of ordinary asphyxia. The individual becomes suddenly weak and insensible; falls down; and either expires immediately, or, if he is fortunate enough to be quickly extricated, he may revive in no long time, the belly remaining tense and full for an hour or upwards, and recovery being preceded by vomiting and hawking of bloody froth.[2033] When the noxious emanations are less concentrated, several affections have been noticed, which may be reduced to two varieties, the one consisting of pure coma, the other of coma and tetanic convulsions. In the comatose form, the workman seems to fall gently asleep while at work, is roused with difficulty, and has no recollection afterwards of what passed before the accident. The convulsive form is sometimes preceded by noisy and restless delirium, sometimes by sudden faintness, heaving or pain in the stomach, and pains in the arms, and almost always by difficult breathing, from weakness in the muscles of the chest. Insensibility, and a state resembling asphyxia rapidly succeed, during which the pupil is fixed and dilated, the mouth filled with white or bloody froth, the skin cold, and the pulse feeble and irregular. At last convulsive efforts to breathe ensue; these are followed by general tetanic spasms of the trunk and extremities; and if the case is to prove fatal, which it may not do for two hours, a state of calm and total insensibility precedes death for a short interval.[2034] When the exposure has been too slight to cause serious mischief, the individual is affected with sickness, colic, imperfectly defined pains in the chest, and lethargy.[2035] The appearances in the bodies of persons killed by these emanations are fluidity and blackness of the blood, a dark tint of all the internal vascular organs, annihilation of the contractility of the muscles, more or less redness of the bronchial tubes, and secretion of brown mucus there as well as in the nostrils, gorging of the lungs, an odour throughout the whole viscera like that of decayed fish, and a tendency to early putrefaction.[2036] Chaussier in his experiments also remarked in animals, that when a plate of silver or bit of white lead was thrust under the skin it was blackened.[2037] Dr. Percy could not detect the gas in the brain of animals killed by inhaling it. These extraordinary accidents may be occasioned not only by exposure to the vapours from the _fosses_, but likewise by the incautious inhalation of the vapours proceeding from the bodies of persons who have been asphyxiated there. Sickness, colic, and pains in the chest, are often caused in the latter mode; and Hallé has even given an instance of the most violent form of the convulsive affection having originated in the same manner.[2038] In order that the reader may comprehend the exact cause of these accidents,—as it is not easy for an Englishman to comprehend how suffocation may arise from the fumes of a privy,—it may be necessary to explain, that in Paris the pipe of the privy terminates under ground in a pit, which is usually contained in a small covered vault, or is at the bottom of a small square tower open at the roof of the house; and that the pit is often several feet long, wide and deep. Here the filth is sometimes allowed to accumulate for a great length of time, till the pit is full; and it is in the process of clearing it out that the workmen are liable to suffer. Hallé has given an interesting narrative of an attempt made to empty one of these pits in presence of the Duc. de Rochefoucault, the Abbé Tessier, himself, and other members of the Academy of Sciences, who were appointed by the French government to examine into the merits of a pretended discovery for destroying the noxious vapours. The pit chosen was ten feet and a half long, six wide, and at least seven deep; and repeated attempts had been previously made without success to empty it. For some time the process went on prosperously; when at last one of the workmen dropped his bucket into the pit. A ladder being procured, he immediately proceeded to descend, and would not wait to be tied with ropes. “But hardly,” says Hallé, “had he descended a few steps of the ladder, when he tumbled down without a cry, and was overwhelmed in the ordure below, without making the slightest effort to save himself. It was at first thought he had slipped his foot, and another workman promptly offered to descend for him. This man was secured with ropes in case of accident. But scarcely had he descended far enough to have his whole person in the pit except his head, when he uttered a suppressed cry, made a violent effort with his chest, slipped from the ladder, and ceased to move or breathe. His head hung down on his breast, the pulse was gone; and his complete state of asphyxia was the affair of a moment. Another workman, descending with the same precautions, fainted away in like manner, but was so promptly withdrawn that the asphyxia was not complete, and he soon revived. At last a stout young man, secured in the same way as the rest, also went down a few steps. Finding himself seized like his companions, he re-ascended to recover himself for a moment; and still not discouraged, he resolved to go down again, and descended backwards, keeping his face uppermost, so that he was able to search for his companion with a hook and withdraw the body.” It was impossible to go on with the operation of clearing out; and the pit was shut up again. The first workman never showed any sign of life; the second recovered after discharging much bloody froth; all the persons in the vault were more or less affected; and a gentleman who, in trying to resuscitate the dead workman, incautiously breathed the exhalations from his mouth, was immediately and violently seized with the convulsive form of the affection.[2039] The same kind of accident has been observed at Paris in the vaults of cemeteries, owing to the same cause,—the disengagement of hydrosulphuric acid and hydrosulphate of ammonia during putrefaction. A remarkable instance is related by Guérard.[2040] Analogous accidents have happened in this country in clearing out drains. In none of the French investigations on this singular subject has any allusion been made to the question, whether the health sustains any injury from long-continued exposure to the gas in very minute proportion. It is probably injurious however. At one time, while in the practice of not using any precautions against inhaling the gas in chemical researches, I used to remark that daily exposure to it in minute quantity caused in a few weeks an extraordinary lassitude, languor of the pulse, and defective appetite. Strohmeyer in the like circumstances was liable to severe headache. Mr. Taylor says that the workmen in the Thames Tunnel suffered severely for some time from a similar exposure. Many of them became affected with giddiness, sickness, general debility and emaciation, then with a low fever attended with delirium, and in the course of a few months several died. No cause could be discovered for their illness except the frequent escape of sulphuretted-hydrogen from the roof. The affection only disappeared, when the communication from bank to bank was completed, so that the tunnel could be thoroughly ventilated.[2041] The presence of hydrosulphuric acid in all such emanations is best proved by exposing to them a bit of filtering paper moistened with a solution of lead. The smell alone must not be relied on, as putrescent animal matter exhales an odour like that of hydrosulphuric acid, though none be present. Workmen ought to be aware that hydrosulphuric acid may be quickly fatal where lights burn with undiminished brilliancy; and that in places where it is apt to accumulate, the degree of purity of the air may vary so much in the course of working, as to be wholesome only a few minutes before, as well as a few minutes after a fatal accident.[2042] In the present place, some notice may be taken of an extraordinary accident, which happened in 1831 near London. Great doubts may be entertained whether hydrosulphuric acid was the cause of it; and while these exist, it is not possible to arrange it under a proper head. It is too important, however, in relation to Medical Jurisprudence, to be omitted in this work; and I take the opportunity of mentioning it here, as the accident was ascribed to hydrosulphuric acid by those who witnessed it. In August, 1831, twenty-two boys living at a boarding-school at Clapham were seized in the course of three or four hours with alarming symptoms of violent irritation in the stomach and bowels, subsultus of the muscles of the arms, and excessive prostration of strength. Another had been similarly attacked three days before. This child died in twenty-five, and one of the others in twenty-three hours. On examination after death, the Peyerian glands of the intestines were found in the former case enlarged, and as it were tuberculated; in the other there were also ulcers of the mucous coat of the small intestines, and softening of that coat in the colon. A suspicion of accidental poisoning having naturally arisen, the various utensils and articles of food used by the family were examined but without success. And the only circumstance which appeared to explain the accident was, that two days before the first child took ill, a foul cess-pool had been opened, and the materials diffused over a garden adjoining to the children’s play-ground. This was considered a sufficient cause of the disease by Dr. Spurgin and Messrs. Angus and Saunders of Clapham, as well as by Drs. Latham and Chambers, and Mr. Pearson of London, who personally examined the whole particulars.[2043] Their explanation may be the only rational account that can be given of the matter. But as no detail of their chemical inquiries was ever published, their opinion cannot be received with confidence by the medical jurist and the physician; since it is not supported, so far as I am aware by any previous account of the effects of hydrosulphuric acid gas. _Of Poisoning with Carburetted Hydrogen._—Of the several species of carburetted hydrogen gas it is probable that all are more or less narcotic; but they are much inferior in energy to sulphuretted hydrogen. Sir H. Davy found that when he breathed a mixture of two parts of air and three of carburetted hydrogen, procured from the decomposition of water by red-hot charcoal, he was attacked with giddiness, headache, and transient weakness of the limbs. When he breathed it pure, the first inspiration caused a sense of numbness in the muscles of the chest; the second caused an overpowering sense of oppression in the breast, and insensibility to external objects; during the third he seemed sinking into annihilation, and the mouthpiece dropped out of his hand. On becoming again sensible, which happened in less than a minute, he continued for some time to suffer from a feeling of impending suffocation, extreme exhaustion, and great feebleness of the pulse. Throughout the rest of the day he was affected with weakness, giddiness and rending headache.[2044] These experiments show that the gas is deleterious. Yet Nysten found it inert when injected into the veins, and what is more to the point, colliers breathe the air of coal mines without apparent injury when strongly impregnated with it. The mixed gases of coal-gas or oil-gas appear likewise to be inert when considerably diluted; for gas-men breathe with impunity an atmosphere considerably loaded with them; and in the course of some researches on the illuminating power and best mode of burning these gases, Dr. Turner and myself daily, for two months, breathed air strongly impregnated with them, but never remarked any unpleasant effect whatever. It would seem, however, from several accidents in France and England, that when the impregnation is carried a certain length, poisonous effects may ensue; and that the symptoms then induced are purely narcotic. The first case, which occurred at Paris in 1830, has been related by M. Devergie. In consequence of a leak in the service-pipe which supplied a warehouse, five individuals who slept in the house were attacked during the night with stupor; and if one of them had not been awakened by the smell and alarmed the rest, it is probable that all would have perished. As it was, one man was found completely comatose and occasionally convulsed, with froth issuing from the mouth, occasional vomiting, stertorous respiration, and dilated pupils. Some temporary amendment was procured by blood-letting, but the breathing continued laborious, and he expired about nine hours after the party went to bed, and six hours after the alarm was given. On dissection the vessels of the brain were found much gorged, the blood in the heart and great vessels firmly coagulated, one of the lungs congested, and its bronchial tube blocked up by a kidney bean. The immediate cause of death in this case is therefore doubtful.[2045] A similar set of cases happened at Leeds in 1838. An old woman and her grand-daughter were found dead in bed one morning at nine o’clock, ten hours and a half after they had been seen alive and well. The air of the apartment was loaded with coal-gas from a leak in a street-pipe ten feet from the bedroom. One body was cold and stiff when found, and the other became rigid very soon. The attitude and expression were calm, the integuments pale, the cerebral membranes natural, the brain itself turgid, and its ventricles distended, in the case of the girl, with an ounce and a half of serosity, the lungs congested, the alimentary mucous membrane red, and the blood every where fluid, and unusually florid, even in the right side of the heart.[2046] Another accident of the same kind, which proved fatal to five individuals, occurred at Strasbourg in 1841. Four were found dead, another survived twenty-four hours after the accident was discovered, and a sixth recovered. It appears from the statement of this person, that the first symptoms were headache and giddiness, then nausea and vomiting, afterwards confusion of ideas, and at length insensibility. General prostration, partial palsy, coma, and convulsions were the leading symptoms after the accident was observed. In the four people found dead the most remarkable appearances were cerebral congestion, redness of the bronchial membrane, accumulation of bloody, frothy mucus in the air tubes, scarlet redness of the lungs, coagulation and darkness of the blood. In the person who was found alive, but did not recover, there was no cerebral congestion, gorging of the air tubes, or redness of the lungs. Professor Tourdes, who reports these cases, ascertained that air containing a fiftieth of coal-gas kills rabbits in twelve or fourteen minutes, and that even a thirtieth proves fatal, though slowly. The gas which caused the accident, and which was prepared from a mixture of water and slate coal, consisted of 22·5 per cent. light carburetted hydrogen, 6·0 bicarburetted hydrogen, 21·9 carbonic oxide, 31 hydrogen, 14 azote, and 4·6 carbonic acid; and by experiment the author found that the most energetic of these gases as a poison is the carbonic oxide, and that the action of the two carburetted-hydrogens is quite feeble.[2047] It is somewhat remarkable that no such accident has ever happened in Edinburgh, where nevertheless coal-gas is more used for purposes of illumination in private houses than in any other city. The fine quality of the gas,—for it contains a mere trace of carbonic acid, and probably less than four per cent. of carbonic oxide,—may be the reason why accidents are not occasioned by it. It is a singular fact, however, that the powerful odour of the gas, when it accidentally escapes in the night-time, generally awakes very soon those who are exposed to inhale it. _Of Poisoning with Carbonic Acid Gas._—Carbonic acid gas is the most important of the deleterious gases; for it is the daily source of fatal accidents. It is extricated in great quantity from burning fuel; it is given out abundantly in the calcining of lime; it is disengaged in a state of considerable purity in brew-houses by the fermentation of beer; it is often met with in mines and caverns, particularly in coal-pits and draw-wells; it may collect in apartments where fuel is burnt without a proper outlet for the vitiated air, or where persons are crowded too much for the capacity of the room. Hence many have been killed by descending incautiously into draw-wells, by falling into beer-vats, and by sleeping before the traps of lime-kilns, or in apartments without vents and heated by choffers. Instances have even occurred of the same accident from sleeping in greenhouses during the night, when plants exhale much carbonic acid; and some dreadful cases have occurred of suffocation from confinement in small crowded rooms. Physiologists, as already remarked, are not quite agreed as to the action of carbonic acid gas,—whether it is a positive poison, or simply an asphyxiating gas. But in my opinion reasons enough exist for believing that it is positively and energetically poisonous. This is perhaps shown by its effects being much more rapidly produced, and much more slowly and imperfectly removed, than asphyxia from immersion in hydrogen or azote.[2048] Thus immersion for twenty-five seconds in an atmosphere of carbonic acid gas has been found sufficient to kill an animal outright; and fifteen seconds will kill a small bird.[2049] But it is more unequivocally established by the three following facts: In the first place, if, instead of the nitrogen contained in atmospheric air, carbonic acid gas be mixed with oxygen in the same proportion, animals cannot breathe this atmosphere for two minutes without being seized with symptoms of poisoning.[2050] Even a much less proportion has the same effect. Five per cent. in the air will affect small birds in two minutes, and kill them in half an hour.[2051] Persons have become apoplectic in an atmosphere of carbonic acid gas, which to those who entered it appeared at first quite respirable.[2052] Secondly, Professor Rolando of Turin having found that the land tortoise sustained little injury when the great air-tube of one lung was tied,—he contrived to make it breathe carbonic acid gas with one lung, while atmospheric air was inhaled by the other; and he remarked that death took place in a few hours.[2053] Thirdly, the symptoms caused by inhaling the gas may be also produced by applying it to the inner membrane of the stomach or to the skin. On the one hand aërated water has been known to cause giddiness or even intoxication when drunk too freely at first;[2054] and the sparkling wines probably owe their rapid intoxicating power to the carbonic acid they contain. And, on the other hand, M. Collard de Martigny has found that, if the human body be enclosed in an atmosphere of the gas, due precautions being taken to preserve the free access of common air to the lungs, the usual symptoms of poisoning with carbonic acid are produced, such as weight in the head, obscurity of sight, pain in the temples, ringing in the ears, giddiness, and an undefinable feeling of terror; and that if the same experiment be made on animals and continued long enough, death will be the consequence.[2055] When a man attempts to inhale pure carbonic acid gas, for example by putting the face over the edge of a beer-vat, or the nose into a jar containing chalk and weak muriatic acid, the nostrils and throat are irritated so strongly, that the glottis closes and inspiration becomes impossible. Sir H. Davy in making this experiment, farther remarked, that the gas causes an acid taste in the mouth and throat, and a sense of burning in the uvula.[2056] I have remarked the same effects from very pure gas disengaged by tartaric acid from carbonate of soda. Hence, when a person is immersed in the gas nearly or perfectly pure, as in a beer-vat, or old well, he dies at once of suffocation. The effects are very different when the gas is considerably diluted; for the symptoms then resemble apoplexy. As they differ somewhat according to the source from which the gas is derived, and the admixtures consequently breathed along with it, it will be necessary to notice separately the effects of the pure gas diluted with air,—of the emanations from burning charcoal, tallow, and coal,—and finally of air vitiated by the breath.