-of certain fevers are so characteristic that an experienced physician, or nurse, can frequently detect the nature of the disease by the odor of the air of the room in which it is confined. This is particularly the case in bilious and rheumatic fevers, influenza, measles, typhus, uræmia, etc.

Moreover, many people exhale peculiar vitiating odors in ordinary health. These are so characteristic often, that the presence of those afflicted with them may be detected by the sense of smell alone. Then there is the strong, rank, African odor, not uncommon to individuals of the lighter-colored race; the fetid odors of ichrosis and osmidrosis, and the sulphureous odors peculiar to many others, any one of which is sufficient. to affect morbificly the air of an apartment in which its subject is confined.

In sick-rooms fever exhalations have been found to exist in appreciable quantities. Moscatti, an Italian physician, is said to have condensed the watery vapor of a hospital-ward at Milan, and found it to be "slimy, and having a marshy smell." "The dust of a ward in St. Louis, Paris, was discovered by Chalvert to contain, in one experiment, 36 per cent. and in another, 46 per cent. of organic matter, which consisted chiefly of epithelium, and when burnt gave an odor of horn. Puscells have been discovered in the air of an ophthalmic ward, and epithelium cells are found in that of all ill-ventilated rooms.* Indeed, there is no end to this field of discovery if one were disposed to work it. The atmosphere, like a great sponge envelope, absorbs every thing noxious or otherwise with which it comes in contact. This is good for the patient, surely, but bad for the air! The fact gives one ample justification for insisting upon thorough disinfection, and the freest, fullest ventilation in the private dwelling and sick-chamber, as well as in the wards of hospitals, schools, churches, and other places where human beings congregate.

There are other evils in the atmosphere, moreover, more subtle than any of those yet mentioned, which play an im

* Huxley and Youman's "Phys. and Hygiene," p. 286.

portant part in the rôle of morbific causes. If a ray of light be permitted to enter through a small opening into a shaded room, no matter how clean and tidy that apartment may be, the air of it will be found to be loaded with all manner of dust and organic debris, much of which is clearly visible to the naked eye. If some of this dust be illuminated on the object glass of a microscope, it will be found to consist of organic and inorganic particles, and many low forms of vegetable and animal life. In fact, the purest atmosphere of which we have any knowledge abounds with powdered rock, iron, silica, marble, the husks of cereals, and the fibres of wood, cotton, hair, wool, etc. Starch grains, also, are present in great profusion. Scarcely an element or product of material nature is unrepresented in the thin, elastic medium which we daily breathe. There are, also, the gases which no microscopic glass reveals, and which are known only by their power to choke us; the aromas, invisible to the eye, but which are strangely manifest to the olfactory sense. Then, there are the various miasmas and parasitic forces invisible for the most part, which, in many localities, fill the air with deadly infec

tion.

Some of these miasmas, notably that of ague and fever, are said to have been ingeniously entrapped and found to consist of fungi, the baleful products of vegetable decomposition. Moreover, the air is frequently infected with elements more deadily than the agents of miasmatic fever; elements which no eye hath seen, and which have yielded to no test, save that of the sensitive perceptions of the vital powers. Aside from the presence of vegetable parasites, little sexless creatures of the order cryptogamia, neither vegetable nor animal, but partaking of the nature of both, and which multiply under favorable conditions with amazing rapidity, there are animal sporules, the product of animal putrefaction, which charge the air with the agents of pestilence and death, and are the presumable source of contagious and infectious diseases. They are too subtle for the analysis of chemical re-agents, the spectroscopic or microscopic tests, and are only certainly known

to us from the effects which their absorption into the blood produces; these being known as cholera, pyæmia, septicemia, the contagious fevers, erysipelas, "yellow jack," etc.

These peculiar germs of disease are multiplied indefinitely within the living economy; the poisonous animalculæ being exhaled in the breath, in the vapors of the body, and in all the excretions of people afflicted with those diseases. Some idea of the mischievous potency of these impalpable fever-germs may be conceived when one reflects that a single breath of air from a room infected with them is sufficient to incite the gravest disease in a person susceptible to their influence. In the case of cholera, M. Delfuysse of the French Academy, claims to have detected the cholera germs in the exhalations of people sick with that disease, and to have demonstrated their animalculæ nature. Be that as it may, the sanitary developments of modern times have clearly established the fact that the infection of cholera exists in the exhalations of those who are afflicted with it, and that if these be duly disinfected—destroyed-the propagation of the disease is surely prevented.

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Then, again, innumerable insects, and still more innumerable germs of insects, infest the air, particularly in tropical latitudes, and the warm seasons of temperate latitudes. Many of these are visible to the unaided eye; many are too small, probably, to be revealed by the most powerful magnifying glass. M. Ponchet maintains that there are "one hundred different species of nicrozoaires, the eggs of which are floating in the air to the extent of 200,000,000 per cubic foot!" These germs of life are probably for the most part innocuous, however objectionable they may be considered to lovers of pure, fresh air. If M. Ponchet's statement be exaggerated 50 per cent. there will still be good grounds to regard the atmosphere as a nutritious medium of the most substantial sort. The hourly consumption by man of a few hundred millions of these eggs must, surely, be of some account in the nutritive economy of human life!

These elements, noxious and otherwise, of the air, are present in different proportion, in different localities, seasons,

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and latitudes. In cities the products of animal decomposition are far more prevalent in the atmosphere than they are in the country; while in the latter the miasmata are naturally more prevalent. The air in manufacturing and mining towns, on the other hand, is overcharged with gases of most deadly properties, the carbonic acid, sulphureous, carburetted, ammoniacal gases, etc.; smoke, watery vapor, and the dust arising from powdered coal and numerous other inorganic substances, the products of the wear and tear of industrial life. The air of the tropics is more largely impregnated with watery vapor, the organic gases, the products of vegetable and animal decomposition, and the countless orders of insects, with their still more countless ova, whose presence is invisible except when in the focus of a powerful microscope.

Some experiments of Dr. Sigerson on the quality of air in diferent localities were communicated to the Dublin Royal Historical Society by that gentleman, not long since, which are possessed of much physiological interest in this connection. "In air from an iron factory," he found, on examination, "carbon, ash, and iron; the latter substance was in the form of little hollow balls, each about two-thousandth of an inch in diameter, the iron being so thin that the light passed through it. In shirt-factory air were found filaments of linen and cotton. Antimony-from the type metal, probably-was discovered in the air of printing-rooms. Stable air was ascertained to contain floating hair and scales; and, in the air through which tobacco smoke was passing, nicotine, the poison of tobacco, appeared in little globules." From these experiments one can easily conjecture what the quality of air would be over grave-yards and vaults, filthy streets and gutters, in closed bed-rooms, the unventilated wards of hospitals, the sick-room of a person suffering from diarrhoea, dysentery, cholera morbus, or typhus. It is said that "Dew collected over rice-fields often contains so much decomposing organic matter as to become putrid after standing for a short time. Exposure to the night air of these localities, in the hot season, invariably produces, in the Caucasian race, malignant and almost incurable

fevers." The invalid, therefore, who changes his northern home to escape the chilling temperature of a northern winter, finds in the atmosphere of the South, it may be, an enemy far more destructive to his bodily constitution than the low temperature and fitful, thermic changes of a New England winter.

That the atmosphere in its purest condition is numerously inhabited by living organisms seems to be demonstrated beyond all rational dispute. The labors of Redi in the seventeenth century, Spallanzani in the eighteenth, and Schevann, Schultze, Helmholtz, Ponchet, Cohn, Sanderson, Huxley, and others, in the nineteenth, have long since placed the subject beyond rational controversy; but it remained for M. Pasteur, the eminent French microscopist, in a series of brilliant experiments, in 1862, to ascertain the proportion in which they were present in the air.

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The experiments of M. Pasteur have been followed up by others both in England and on the Continent with remarkable conformation. The number of these organisms which Dr. Angus Smith and Mr. Dancer of England claim as mostly recognizable in twenty-five hundred litres of Manchester air, by no means the worst in England, they estimate as high as thirty-seven and a half millions, or about seventy-five thousand of the little creatures to one gallon of air! This proportion very variable, depending upon the seasons, the purity of the air, and the distance from the earth and the abodes of organic life. M. Pasteur found their presence in a maximum proportion at the sea-level, and growing less and less in proportion. as he advanced in elevation. Thus at Montanvert, near the Mer. de Glace, at an elevation of two thousand metres, a minimum of the organisms was discoverable.† found in an atmosphere of average purity, by Messrs. Smith and Dancer, is much less than that estimated by M. Ponchet already quoted. But it will do!

* Well's Chemistry, p. 225.

+ Vide Quar. Jour. Science, No. xxxviii., p. 232.

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