During the 18th c. many important steps were taken for the improvement of the pub lic health. Under a proper system of dcaina7e, ague became eradicated from exten sive fenny districts; and with a knowledge of the therapeutic properties of cinchona hark and arsenic, we can cut short the, disease when it appears. Scurvy* was all but blotted out of the list of diseases that proved most fatal to our sailors; and vaccina tion:incomparably the greatest discovery yet made in this department of science, was the crowning achievement of the century.f The first outbreak of cholera in this coun try in 1832, lamentable as it was in itself; was productive of much benefit in directing the public mind to the all-important subject of the prevention or repression of dis ease. It was impossible to ignore the fact that, while the poor, unventi lated and undrained hovels. fell victims to this new and ill-understood disease in thousands, the middle and higher classes were comparatively safe. All investigations into the dwellings and domestic habits 'of the lowest class kof the population revealed a condition of things of which the general public had no conception. A new poor law was consequently passed in 1834, and a commission was appointed to investigate and report upon its working. The Report on the Sanitary Condition of the _Laboring Pbpu ktion of Great Britain, published in 1842, and mainly treating of time sanitary the poor and of the character of their dwellings, may be regarded, as pre' :_laminer I well observes, as "the true starting-point of modern sanitary legislation,.'', A " health of towns commission," which was soon after appointed, gave an two valuable reports in 1844 and 1845; and subsequently a metropolitan sanitary commission published reports in the years 1847 and 1848. These reports will form a lasting memorial of the labors of Mr Chadwick and his able co-operators. Nor, in this rapid glance at the history of sanitary science, can the name of Dr. William Farr be omitted, who—again to quote Dr. Gairdner's words—" found the facts of this science in a state of almost hopeless and aimless confusion, and has not only added immensely to their number and value, but has brought into them light, harmony, order, and, for the first time in the history of the science, a determinate mathod. and an approach to scientific exactness." By his system of calculating death-rates he has placed an easy and useful method at the ser vice of his professional brethren, while, by the formation of life-tables, he has greatly facilitated the operations of life-assurance.
We now pass on to the consideration of the most important sanitary agents, begin ning with Ant. Under this head we have to consider (1) the amount of air necessary for the full performance of the respiratory process; (2) the means of ascertaining when air is impure, or, if impure, what substances are mixed with it: (3) the means of purify ing, contaminated air; and (4) Biel diseases due to deficiency in the quantity, and altera tions in the quality of the air.
(1) The ,first question can be answered both by calculation and experiment. By cal culation, Dr. Parkes finds that 2,082 cubic ft. of air must be supplied per head per hour, so to dilute the products of respiration and transpiration from the sound body, as to keep the air always pure and fresh (see his Manual of' Practical hygiene, 1864, p. 65). From numerous experiments in which the outflow of air was measured, and the carbonic acid simultaneously determined, he found that at least 2,000 cubic ft. per hour must he given to keep the carbonic acid at its normal level of .5 or .3 in 100 volumes, and to remove the odor humanus or fetid smell of animal matter. Gen. Morin. in his Rapport de In Commission sal. le Cita off tge et la Ventilation des Bikimens du Pa'ais de Justice, 1860, gives results in close accordance with those of Parkes, assigning the following as the relative hourly amounts of fresh air (expressed in cubic feet) per head in temperate climates: in barracks, at 1059 by day, and 2,118 by night; in work shops, prisons, and theaters, 2.118; in schools, 1059; and in hospitals, 2,825, increased to 4,236 during the hours of dressing the surgical cases, and 5,650 during epidemics.* In mines, if it is wished to keep up the greatest energies of the men, 6,000 ft. of air per hour must be allowed. It may be incidentally mentioned that a horse requires 2,460 ft. per hour at the least. It is difficult to lay down any rules regarding the amount of fresh air required in sickness. The vitiation of the air by the products of combustion of gas, candles, lamps, etc., must not be overlooked. 'For every cubic foot of gas that is burned, 180J cubic ft. of air are required to keep the air pure, unless gaseous prod ucts are carried off in a special channel, such as is now frequently attached to gas fittings. A pound of oil burned in a lamp may be regarded as equivalent to 10 cubic ft. of gas, so far as the deterioration of the air is concerned. (For these facts we are indebted to Dr. Parkes,)
(2) The composition of pure air is sufficiently described in The impurities in air may be divided into: (a) suspended matters, (b) gaseous substances, and (e) special int:prides. Amongst suspended matters are, according to Pastenr.and others, numerous and universal germs of organic beings, both animal and vegeta ble, as of vibriones, bacteria, and monads; pollen, spores of fungi, mycoderins, mucedones, etc. Minute particles of finely comminuted inorganic matter are also often taken up by currents of air, and remain in suspension. These are proba bly altogether harmless. The works of man more seriously affect the air :n a hygi enic point of view. Particles of coal and of half-burned carbon (smuts), starch-cells (from bakeries and bread), and, when certain trades are carried on, cotton fibers, hairy particles of wool, of stone, of iron, etc., may, when constantly inhaled, give rise to the production of special diseases of the lungs and stomach, In the air of badly-kept hos pital wards, pus-cells and epithelial cells are often to be detected. Most physicians now believe that the specific poisons of small-pox, scarlet fever, and measles, which are derived from the skin and mucous membrane, consist of molecular organic matter, which, although as yet undetected, must pass into the air: and the same remark applies to the so-called germs of typhoid fever (see the article on TYPHUS AND TYPHOID FEVERS) and cholera, which are thrown off by the intestinal mucous membrane, and subsequently become dried and capable of aerial suspension. Amongst gaseous matters, which merely pass into the atmosphere either from natural causes or manufactories, are various com pounds of carbon, sulphur, chlorine, nitrogen, and phosphorus, with oxygen and hydrogen, which it is unnecesary here to enumerate. Besides the gases formed by the union of the above-named elements, we must notice organic vapor from decomposing animal matters and sewers, which last has been found by Odling to be carbo-ammont ilea]. Amongst special smpurities, those caused by respiration are the most important, An adult man, under ordinary conditions, gives off, in 24 hours, from 12 to 16 cubic ft. of carbonic acid by the lungs, and a certain additional quantity, not determined. by the skin. Watery vapor, ranging from 25 to 40 ounces, also passes off daily from the skin and lungs, together with an undetermined quantity of organic matter, which is partly suspended (as particles of epithelium, etc.), and partly made up of organic vapor. This vapor, when collected and condensed front a large volume of respired air, is found to be nitrogenous, and has a very fetid smell. Here there is a most powerful source of vitiation, regarding which numerous chemical analyses have been made; for details regarding which we may refer to Parkes, op. cit. pp. 70-77; Gaird•er, op. cit. p. 6t4; and Mapother's Lectures on Public Health, 2d ed., pp. 40-61. '1 here is a condition of the Atmosphere to which various observers, and especially Pasteur, have directed attention, whielfrequires a passing remark. It is what may he termed the fermentative condition, and depends upon the universal presence iu the air of countless germs of vegetables and infusoria. It is possible that this atmospheric condition may be concerned in some of the zymotic diseases. Dr. Salisbury, an American physician, endeavors to show that the poison of measles is due to a fungus which grows on rotten straw; another American physician, Dr. Flint, " has tamest fully demonstrated that the spores of palmella cause ague."—i'llapother, op. cit., p. 441, etc. The presence of a cholera fungus, which has been recently proved to exist in the evacuations of all cholera patients, gives, as will be seen from Mr. Simon's report of the Weimar conference,* a hint as to the probable cause of that disease. Bearing on the same subject is the fact, lately noticed by Davaine, that the splenic apoplexy of sheep is owing to the presence of bacteria in the blood, and that sheep, rabbits, and horses can be inoculated by transferring into their coicuiatiun, the bacteria, which are extremely thin rod-like organisms, varying in length from an inch. The same observer lies just found (as we learn from the Parisian Medical Intelligence,".in the Lancet for Jan. 4,1868) that bacteria are to be town! in all carbuncular diseases of any form whatever; that the superveusion of these little beings in the spleen, the lungs, and the blood precedes the occurrence of morbid phenomena; and that the carbuncular blood ceases to be contagious as soon as the bacteria have dis appeared; and hence he feels justified in regarding them as the cause of carbuncle. Another French observer, M. Poulet, has just detected myriads of itifusotia (monas termo and others) in the breath exhaled in whooping-cough. If one contagious disease can be proved to be connected with the germs occurring in the air, it is almost, a cer tainty that similar diseases must arise from corresponding causes.