(b) The most important gaseous matters in the air likely to produce diseases are car-• bonic and and carbonic oxide. The normal quantity of carbonic acid in the air being regarded as .5 in 1000 volumes, "it produces fatal results when the amount reaches 50 per 1000 volumes; mid at an amount much below this,. 15 or 20 per 1000, it product s in sonic persons, at any rate, severe headache." Dr. de Chaumont, assistant professor of hygiene at Nethly, has published a valuable paper in the Lancet for Sept., 1860, in which he shows how the amount of air necessary to reduce the carbonic acid of respiration to a given standard could be calculated; and in the Edivborgh Medical Journal for May 180, he hay given extended formula for calculating most of the problems connected vith ventilation. Amongst the most important of his conclusions Incr the following: (1) We cannot safely accept a lower standard of put ity than .00 per cent of carbonic acid, (2) Uniform diffusion being supposed, we cannot preserve this standard with a less delivery of fresh air than 3,000 cubic ft. per head per hour. (3) We must provide an air rprree which will admit of the delivery of 3,000 cubic ft. per head, and at the same time preclude the necessity of changing the air so often as six times per hour, for which condition at minimum of 1000 cubic ft. is absolutely necessary.* Casbon:c oxide (q.v.), which is often developed in association with carbonic acid, is far more actively poisOnous than carbonic acid. An atmosphere containing per cent kith d small birds In three minutes; and when 1 per cent was pie si nt they died in half this time (1.ethelly). Por the effect of other gaseous matters, as sulphuretud hydrogen, carbureted hydi ogen, sulphurous acid gas, hydrochloric acid gas, etc. we must refer to any of the more elab orate works on this subject.
(c) The impurities from several co-existing agents next claim attention. In point of fact, these are the impurities with which we have practically almost always to deed, and it is very probable that a knowledge of the actions of two or more i elated noxious agents might lend us to very incorrect conclusions regarding the composite effect that is Lethally produced. When air is vitiated by respiration, it is popularly believed that the ( arbonic acid gas is the chief poisonous agent; and that the fatality in such well-known cases as the Black Hole (q.v.) of Calcutta. the prison in which the Austrians were placed titer the battle of Austerlitz, the steamer Londonderry, etc., is simply due to the action of this gas. The true poisonous agencies in these instances are the organic matter, which is always found in air rendered fetid by the prolonged respiration and cutaneous exhalation of a crowd of human beings. and the deficiency of the oxidation, and the consequent increase of putrescent matter in the hodv (see Carpenter's Human Physiology, 1801. p. 304). Putting aside these extreme cases, _which are of rare occurrence, we have abundant evidence in the reports of the Health of Towns commission, and elsewhere, that ., tie continuous inhalation of an atmosphere moderately vitiated from respiration has an injurious effect on the health. The aeration of the blood is imperfectly effected, and the nutrition generally is more or less interfered with Although impure air has long been vaguely regarded as a cause of phthisis, it is only (luring the present century that the fact Luis been placed on unquestionable authority. It may now be regarded us lished that not only phthisis but other lung-diseases may have their origin in breathing an atmosphere contaminated by respiration. The subject is one of such vital inmortance that. we shall adduce the very strong evidence of Dr. Parkes. who most distinctly prove. that the prevalence of pin hisis among our troops is in a direct ratio to the impurity of the air in the barracks. "A great amount of phthisis used to prevail," he observes. "int the most varied stations of the army, and in the most beautiful climates. in Gibraltar, Mika, Ionia, Jain:ilea, Trinidad, Bermuda, etc., in all which places the only common condition was the vitiated atmosphere which our barrack-system everywhere produced. And, as if to clench the argument, there has been of late years a most decided decline in phthisical cases in these stations, while the only circumstance which has notably changed in the time has been the condition of the air. So also the extraordinary amount of consumption which prevails in the men of the royal and merchant navies, and which, sonic men-of-war, has amounted to a veritable epidemic, is in all probability attributa ble to the faulty ventilation."—Op. cit., pp. 91, 02. A considerable amount of evidence in support of this view is afforded by comparative pathology. The t xtraerdinary mor tality of plithisis among the inhabitants of the old monkey-house in the zoological gar dens was found to be dae to overcrowding and bad veutilation; and now, iu their present airAcresidence, the inhabitants are no 'longer prematurely cut off. The overcrowding to
which cows in large towns are subjected leads to the great amount of pulmonary disease among these animals; while horses, which in the worst stables have more free air than cows, rarely suffer. Not only are pulmonary affections induced by the prolonged respi ration of air partially vitiated by organic exhalations, but such an atmosphere seems to favor the spread of several well-known specific diseases, as typhus, plague, small-pox, scarlatina, and measles.
Hitherto we have simply considered the effect of breathing an atmosphere vitiated by the exhalations given off by persons in ordinary health; if we now pass to the consider ation of the air of a crowded hospital-ward, we shall find the organic matter not only more abundant, but at the same time far more noxious. The convalescence of patients is much retarded by their being kept in such an atmosphere (see CONVALESCENT Hos rrraLs). When the air has absorbed a certain amount of organic impurity, its respira tion is very liable to give rise to erysipelas an I bespital gangrene. 45'iwe•s and old C383 pools, when opened, give off sewage-gas containing carbonic acid. sulphureted hydrogen, sulphide of ammonium, and putrid organic vapor. A case is given in the first volume of the Health of Towns Report, which forcibly illustrates this fact. When a privy con nected with a school at Clapham was cleaned out. 23 of the children were seized with violent vomiting and purging, headache, great prostration, and convulsive muscular twitchings; and two of them died within 21 hours. S.nver-inen are more liable to typhoid and typhus fever than other persons; but night-men and scavengers do not seem liable.to any special disease. The effect of dilated sewe•-gas from bad drainage on the "weld' of the population at large, is a distinct question, into which we have no, space,to enter, further than to remark that typhoid zuhl diarrhea are commonly induced by the escape of this gas through our drains and water-closets into our houses. The effects. of the impurities Lrising from manufactories of variens kinds are of course extremely varied; and the subject is so extensive a one that it must be touched upon very briefly. Sulphurous aail sulphuric acid are given off from vitriol and c ipper-smalting works; hydrochloric acid from alkali-works; arsenical fumes and sulphurous acid from copper and lead smelting furnaces; catboaic acid au.1 carbonic oxide from cement-works. etc. Soap and candle manufactories, if not well superimteuded, yield various gases of a ran cid smell, and even that powerful irritant, acroleine. Gas-works in which the wet-lime process of purification is adopted, often evolve sulphureted hydrogen to such a degree as to become a nuisance injerious,to health. Manure-works usually evolve more or less disgusting smells according to the basis operated on and the mode of preparation. No bad effect on the health has, so far as we know. been observed in this country from the gases given off by such works, and the exhalations from the manufactories of vondrefte, Which is dry faecal matter, are positively declared, by several of the highest French authorities, to exercise no injurious action either on man or vegetation; 'hut the emi nent French hygienist, Parent Duchatelet, relates two cases in which pondrette under went fermentation on board ship; and in one of these eases the vessel lost half her crew (number not stated); while in, the other, all on board (five) suffered from intenso headache, pain in the limbs, vomiting, prostration, and (in two cases) diarrhea. The air of old graveyards, when they are disturbed, often gives rise to epidemics of fever; but the effect of the effluvia of comparatively recent putrefying human bodies is much more decided. Numerous cases are recorded of asphyxia and various forms of fever arising from the exhumation and disturbance of bodies. ,How far the effluvia , 'rising from daughter-hoases and kna-ekeries are injurious to health is an open ques .on. There is very strong general evidence that the men employed at Montfancon where, however, the ventilation is excellent, and no putrid matters are allowed to remain) enjoy good health; and Tardieu, from a late re-examination of the point, con firms the old conclusion, except so far as glanders and malignant pustnle are con cerned. The danger of breathing the air ql marslies also requires notice. Malaria seems not only to occasion intermittent and remittent, fevers, but diarrhea and pure dysentery. Organic matter to the amount of eight grains has been obtained from 1000 cubic feet of air collected over marshes; and it is worthy of notice that it has jest the same chemical characters as the organic matter exhaled from the lungs, [liming red with nitrate of silver, yielding ammonia when treated with lime, and blackening sul phuric acid when drawn through it. Sec Mapother, op. cit., p. 87.