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a winter's night, have been destroyed by the respiration of these gases. The discovery of a dead body in such a situation would commonly suffice to indicate the real cause of death; but a practitioner ought not to be the less prepared to show that there existed no other apparent cause of death about the person. It is obvious that a person might be murdered, and the body placed subsequently near a kiln by the murderer in order to avert suspicion. If there are no marks of external violence, the stomach should be carefully examined for poison; in the absence of all external and internal injuries, medical evidence will avail but little; for a person might be criminally suffocated, and his body, if found under the circumstances above stated, would present scarcely any appearances upon which a medical opinion could be securely based. An accident is related by Foderé, in which seven persons of a family were destroyed, in consequence of their having slept on the ground-floor of a house in the courtyard of which a quantity of limestone was being burnt into lime. They had evidently become alarmed, and had attempted to escape; for their bodies were found lying in various positions. The courtyard was enclosed, and the carbonic acid had poured into the apartment through the imperfectly closed window and door. A man died three days after being exposed to the vapours of a lime-kiln. (Guy's Hosp. Rep.' 1839.)

The vapours of brick-kilns are equally deleterious, the principal agents being carbonic acid and carbonic oxide; although, according to the state of combustion of the fuel, ammonia, hydrochloric acid, sulphuretted hydrogen, and sulphurous acid may be also evolved. In 1842, two boys were found dead on a brick-kiln near London, whither they had gone for the purpose of roasting potatoes. Although the cause of death in the two cases was clearly suffocation, in one instance the body was extremely livid, while in the other there was no lividity whatever. Such accidents are frequent.

Brick-kilns are frequently the subjects of injunction or action on the ground of their being public nuisances. There can be no doubt that the vapours which they give off are noxious, i.e. injurious to health as well-as offensive, and that they create great discomfort. They contaminate the air, and render it unfit for respiration. In contested cases of this kind, the medical and general evidence is often very conflicting. In a case of this kind, Re Tassell, 1867, Wood, V.C., in granting an injunction, justly observed that brick-burning was not the less a public nuisance because certain individuals were so peculiarly constituted as not to object to it, the real question being how far it affected the generality of persons of ordinary habits. The vapours of cement-kilns are quite as noxious as those of brickkilns: carbonic and sulphurous acids predominate in them.

CONFINED AIR.

Symptoms and effects.-An animal confined within a certain quantity of air, which it is compelled to breathe, will soon fall into a state of lifelessness. A human being in the same way may be suffocated, if confined in a close apartment where the air is not subject to change or renewal, while the products of respiration are accumulated; and the effects are hastened when a number of persons are crowded together in a small space. The change which air, thus contaminated by breathing, undergoes, may be very simply stated. The quantity of nitrogen in 100 parts will remain nearly the same; the quantity of oxygen will probably vary from 8 to 12 per cent., while the remainder will be made up chiefly of carbonic acid. If many persons are crowded together the air will acquire a high temperature, and will be saturated with aqueous vapour which contains decomposing animal matter derived from the lungs and skin. It is evident that air which has been

contaminated by continued breathing will operate fatally on the human body, partly in consequence of its being deficient in oxygen, and partly from the noxious effects of the carbonic acid contained in it. The proportion in which carbonic acid exists in respired air is subject to variation: according to the experiments of Allen and Pepys, it never exceeds 10 per cent. by volume of the mixture, how frequently soever it may have been received into and expelled from the lungs. The influence of respiration on air may be thus stated:-An adult consumes from one gallon (2774 cubic inches) to two gallons of air per minute, and the air expired contains from 4 to 5 per cent. of carbonic acid; but when a person continues to breathe the same air the proportion of carbonic acid expelled is reduced at each successive respiration. When the amount in air has reached 10 or 12 per cent. no more is thrown off by the lungs, and the blood is no longer depurated. For healthy existence a human being requires 20 cubic feet or 125 gallons of air per hour. A common candle will consume as much as two gallons of air per minute, or render that quantity of air unfit for breathing. Dalton found that the air in crowded rooms contained about 1 per cent. of carbonic acid, the atmospheric proportion being therefore increased twentyfold. It is certain that insensibility and death would ensue in a human adult before the whole of the oxygen of the confined air had disappeared; but the opportunity can rarely present itself of analysing such a contaminated mixture, and hence it is impossible to specify the exact proportion in which carbonic acid would exist when the confined air proved fatal to persons who had breathed it. Lassaigne has shown, by direct experiment, that the carbonic acid in the air of close rooms is not collected on the floor, but equally diffused throughout. The whole mass of air is, in fact, vitiated, and requires renewal by proper ventilation. (Med. Gaz.' vol. 38, p. 351; see also Rep. on Mines,' 1864, App. B, p. 196, and 'Chem. News,' Feb. 17, 1865, p. 79.)

COAL-GAS. CARBIDES OF HYDROGEN.

"Coal-gas is a compound which when breathed acts directly as a poison. Many fatal accidents have occurred from the breathing of air contaminated with it. Its composition is subject to much variation, according to circumstances. Mitscherlich found that it was principally composed of marsh gas, hydrogen, and carbonic oxide, in the proportion of 66 per cent. of the first, 213 of the second, and 11 of the third. Tourdes found that the proportions of marsh gas and carbonic oxide were nearly equal, i.e. about 22 per. cent. An analysis of coal-gas, as supplied in London, shows that it contains per cent.-of hydrogen, 46'43; of marsh gas, 3.89; carbonic oxide, 562; olefiant gas, 3.86; watery vapour, 2:48; nitrogen, 2:22; carbonic acid, 46. Some consider that carbonic oxide is the poisonous principle; but there is little doubt that the heavier hydrocarbons also have a noxious influence.

Symptoms and appearances after death.-The symptoms produced by coal-gas, when mixed in a large proportion with air, are-giddiness, headache, nausea with vomiting, confusion of intellect, loss of consciousness, general weakness and depression, partial paralysis, convulsions, and the usual phenomena of asphyxia. The appearances after death will be understood from the following cases. A family breathed for forty hours an atmosphere contaminated with coal-gas which had escaped from a pipe passing near the cellar of the house in which they lodged. On the discovery of the accident four of the family were found dead. The father and mother still breathed; in spite of treatment the father died in twentyfour hours, but the mother recovered. When the five bodies were inspected, there was a great difference in the appearances; but the principal

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changes observed were, congestion of the brain and its membranes-the pia mater (inner membrane) being gorged with blood, and the whole surface of the brain intensely red. In three of the cases there was an effusion of blood (coagulated) on the dura mater and in the spinal canal. The liningmembrane of the air-passages was strongly injected, and there was spread over it a thick viscid froth, tinged with blood; the substance of the lungs was of a bright-red colour, and the blood in the vessels was coagulated. ('Ann. d'Hyg.' Jan. 1842.) In two cases ('Guy's Hosp. Rep.' No. 8), there was found congestion of the brain and its membranes, with injection of the lining-membrane of the air-passages; and the blood was remarkably liquid. An aged woman and her granddaughter, who had been annoyed by the escape of gas during the day, retired to bed; and they were found dead about twelve hours afterwards. In January, 1883, a man retired to bed, leaving the gas-jet alight. The gas was subsequently turned off at the meter, and turned on again in the morning. He was found dead from suffocation. This is a not infrequent accident.

A gas-fitter accidentally breathed coal-gas while connecting a tube with a meter. The skin was cold, the cornea glazed, and the face pale and placid; there was some froth about the mouth, the pupils were rather dilated, and the limbs supple. There was a strong smell of gas in the place. He was working in a closet, and he was found insensible on the top of a pair of steps in a sitting posture-his head on one side, his arms hanging down, and his back leaning against the wall, in the attitude in which he had been engaged at his work. He had evidently died quietly and placidly on his seat, and had made no attempt to descend the steps. He was last seen alive an hour before he was found dead, and he no doubt died rapidly from the inhalation of the gas. An inspection of the body was made twentyfour hours after death. Externally, the skin of the face and upper part of the body was pale, rigidity was well-marked, and there was general lividity of the back of the body as well as of the limbs. The blood was everywhere fluid. The brain and its membranes were not congested, but were rather pale than otherwise; the ventricles contained a pale serum. The brain and cerebellum were healthy in structure. There was a strong odour of coal-gas on exposing the brain. The lungs were of a dark-red colour, and did not collapse on raising the sternum; they were dark at the back of the lobes from gravitation of blood; and their structure was healthy. The windpipe and bronchi contained frothy mucus in some quantity. powerful odour of gas was perceived on compressing the lungs. The heart was healthy; the right cavities were distended with blood, the left were nearly empty; the blood was everywhere black. There was congestion of the abdominal viscera, but no other unusual appearance. ('Med. Chir. Trans.' 1862, 45, 103.)

A

In the case above related, the effects produced by coal-gas were owing to the long-continued breathing of it in a diluted state. The quantity contained in the air of the rooms must have been very small: in the first cases it was probably not more than 8 or 9 per cent., because at a little above this proportion the mixture with air becomes explosive; and there had been no explosion in this case, although in the apartment in which the persons were found dead a stove had been for a long time in active combustion, and a candle had been completely burnt out. In the second cases those who entered the house perceived a strong smell of coal-gas, but still the air could be breathed. A set of cases occurred at Leeds, in 1870, in which four persons lost their lives from the breathing of coal-gas in a diluted state. The gas main had in it a crack from which the gas had leaked on each side of the party-wall between the two houses in which the deceased persons lived, The air of the bedrooms had been gradually

VOL. II.

I

impregnated with gas, causing loss of muscular power and insensibility, and they appeared to have passed from sleep into death without making any effort to escape. The gas produces, very gradually, anesthesia followed by fatal narcotism. A slight leakage into a bedroom is sufficient to produce fatal effects. In 1869, a man was found dead in bed, and there was a strong smell of gas on entering the room. It had escaped, while the deceased was sleeping, from some small holes which were accidentally made in the gas-pipe by driving nails into a plank of the floor. On inspec tion, the brain was found congested and the lungs engorged with blood throughout their substance. The lining-membrane of the stomach was of a deep red colour. The other organs were healthy. The cause of death was the breathing of coal-gas in a diluted state. The gas had only been turned on at 6 A.M., while the man was sleeping, and he was found dead at 10 A.M. He had then probably been dead about two hours, and had passed rapidly from sleep into death by breathing this poisoned atmosphere. This gas may destroy life if long breathed, although so diluted as not to produce any serious effects in the first instance. Insensibility may, however, be an early symptom in a very diluted atmosphere, and unless the person is speedily removed into fresh air he will die. In one case, a man entered a large open pipe four feet in diameter, which had been used for gas, to look for a leak. He thought all the gas had been let off. On entering the pipe he perceived a strong smell, and remembered nothing further. He was taken to the infirmary in an unconscious state, suffering from violent muscular contractions. He recovered in two days. ('Lancet,' 1870, 2, p. 816.) The breathing of this gas renders a man entirely powerless to give any alarm or make any effort to save himself. Stupefaction, and a loss of all muscular power, speedily follow the inhalation of diluted coalgas. ('Ann. d'Hyg.' 1870, 1, 60.)

Coal-gas owes its peculiar odour chiefly to the vapour of naphtha, which indicates its presence thus. The odour begins to be perceptible in air when the gas forms only the 1,000th part; it is easily perceived when forming the 700th part; but the odour is strongly marked when it forms the 150th part (Tourdes). Some persons can detect 1-10,000th part in air by the sense of smell. In most houses in which gas is burnt, the odour, owing to leakage, is plainly perceived; and it is a serious question whether health and life may not often be affected by the long-continued breathing of an atmosphere containing but a very small proportion of gas. The odour will always convey a sufficient warning against its poisonous effects. It should be known that this gas will penetrate into dwellings in an insidious manner. In one case (Guy's Hosp. Rep.' No. 8, see p. 113, ante), the pipe from which the gas had escaped was situated about ten feet from the wall of the bedroom where the women slept: the gas had permeated through the loose earth and rubbish, and had entered the apartment through the floor. In several other cases coal-gas has thus destroyed life by leakage into bedrooms. (See 'Lancet,' 1872, 1, p. 32.)

It is impossible to determine exactly what proportion of this gas in air will destroy life. An atmosphere containing from 7 to 12 per cent. has been found to destroy dogs and rabbits in a few minutes; when the proportion was from 1 to 2 per cent. it had little or no effect. With respect to man, it may destroy life if long breathed when forming about 9 per cent., i.e. when it is in less than an explosive proportion. (Brit. and For. Med. Rev.' vol. 20, p. 253; Ann. d'Hyg.' 1830, 1, 457; 1870, 1, 63.) Aldis observed that in ordinary coal-gas mixed with air, rats were rendered insensible in half a minute, and died in a minute and a half or two minutes. There was before death spasmodic action of the diaphragm. The gas was allowed to enter slowly into a bell-jar of air in which the animals were placed. (Med. and Chir. Trans.' 1862, 45, 100.)

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Analysis. The circumstances under which the accident occurs will generally suffice to establish the nature of the noxious agent. Coal-gas burns with a bright-white light, producing carbonic acid and water. A taper should be cautiously applied to a small quantity; since, when the gas is mixed with the air in the proportion of from 11 to 14 per cent., it is dangerously explosive. For this reason no lighted candle should be taken into an apartment where an escape has occurred, until all the doors and windows have been for some time kept open, and the smell of gas has entirely disappeared. (See 'Med. Gaz.' vol. 42, p. 343.) The combustion of the gas, or its explosion with air, is a sufficient test of its nature; the peculiar odour and the want of action on a salt of lead, if the gas is pure, will distinguish it from sulphuretted hydrogen.

NITROUS OXIDE.

Sir Humphry Davy was the first to show by experiments on himself that, with certain precautions, nitrous oxide gas might be breathed without danger to life, and that it had the effect of producing an agreeable species of intoxication. He breathed in one experiment three quarts, in another nine quarts, and in a third twenty quarts of unmingled nitrous oxide. (Brewster's 'Nat. Magic,' p. 345.) He suffered no injury from inhaling these quantities, either at the time or subsequently. The author has seen it taken in quantities of about two to three quarts in more than five hundred cases, without any ill effects following. In these cases the first symptoms were pallor of the countenance, lividity of the lips, and a staggering gait, followed by violent muscular exertions. These effects passed off in from three to five minutes. In a few cases a feeling of exhaustion, with headache and pain in the chest, followed the inhalation. Brewster describes, on the authority of Silliman, two cases in which some remarkable after-effects were produced. A young man who took nitrous oxide for the sake of experiment was seized with delirium, and after making some violent exertions, fell exhausted on the ground: convulsions followed, and he uttered the most piercing shrieks and cries. These symptoms continued for two hours: he was perfectly unconscious of what he was doing, and was in every respect like a maniac. On recovery he stated that his feelings vibrated between the most perfect happiness and the most consummate misery. He recovered in three or four days, suffering only from a feeling of fatigue and exhaustion. The other case was that of a man of mature age and of a grave character. He had been suffering from bodily and mental debility just before taking the gas, of which he inhaled three quarts. The consequences were an astonishing invigoration of his whole system, with a great increase of muscular power. effects were felt for at least thirty hours, and in a greater or less degree for more than a week. The gas had a singular effect on the organ of taste The gas itself, as is well known, has a sweetish taste, and according to Silliman, he, after inhaling it, had acquired a taste for such things only as were sweet. For several days he ate chiefly sweet cake, and took sugar and molasses on his bread and butter, as well as upon his meat and vegetables. Even after eight weeks had elapsed, he was found pouring molasses over beef, fish, poultry, cabbage, potatoes, or whatever animal or vegetable food was placed before him. It was noticed by his friends that his health and spirits had undergone a remarkable change. (Brewster's 'Nat. Magic,' p. 349.) In these cases the gas was diluted with air when inhaled.

These

Nitrous oxide as an anaesthetic.-Passing from these exceptional cases, no administration of the gas proved fatal until the year 1873. Nitrous oxide has been, and is, employed extensively by oculists, dentists, and surgeons as a substitute for the vapour of chloroform and ether, and,