Page:Popular Science Monthly Volume 40.djvu/837

called ozone, which is rarely found in the air of towns. Of this gas-mixture (which we call air) we breathe enormous quantities. Of it we breathe in the twenty-four hours, according to Prof. M. Foster, over 2,600 gallons, that is about 425 cubic feet; and as it returns from our lungs the proportions of the mixture are changed, the oxygen being reduced, and the carbonic acid increased.^[1] But in all ordinary cases the quantity of oxygen in a room in which people are meeting is only slightly decreased, while the increase of the carbonic acid is not sufficient to cause bad effects. How, then, arises the mischief?

The truth is that, in taking air into the lungs and breathing it out again, we breathe out with it certain organic poisons. About the existence and presence of these poisons there can be no doubt, though very little is known about their nature. Of them Dr. Foster writes (page 552) that they may be formed in the lungs, or may be products of putrefactive decomposition allied to a class of poisons known as ptomaines, which are found in the system. Dr. A. Ransome (Health Lectures, 1875-76, page 160) says:

The aqueous vapor arising from the breath, and from the general surface of the body, contains a minute proportion of animal refuse matter, which has been proved, by actual experiment, to be a deadly poison. . . . It is this substance that gives the peculiar, close, unpleasant smell which is perceived on leaving the fresh air and entering a confined space occupied by human beings or other animals, . . . and air thus charged has been fully proved to be the great cause of scrofulous or tubercular diseases, and it is the home and nourisher of those subtle microscopic forms of life that have lately become so well known under the title of germs of disease, or microzyms. It is probably the source of a large part of that increase of mortality that seems inevitably to follow the crowding together of the inhabitants of towns.

Galton says (Our Homes, page 497): "This organic matter (given off from the lungs), on an average, may be estimated at thirty or forty grains a day for each adult";^[2] and both Dr. Carpenter and Sir Douglas Galton notice that if breath be passed through water (and then kept in a closed vessel at a high temperature), putrefaction is set up, and a very offensive smell is given off.^[3]

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1. It must be remembered that the act of breathing consists in bringing the blood of the system in contact with air, through a delicate membrane in the lungs. Here an exchange takes place—oxygen being yielded up from the air to the blood, and carbonic acid from the blood to the air.
2. We do not know on what exact grounds this calculation rests.
3. Foster (p. 552) states that "when the expired air is condensed. . . the aqueous product is found to contain organic matter, which, from the presence of micro-organisms, . . . is very apt rapidly to putrefy." L. P. writes: "If a globe be filled with ice and taken into a close, badly ventilated room, the dew which forms outside is found to be contaminated with these organic impurities." L. T. writes: "It is more than likely that it is this animal poison which is the direct cause of typhus fever as that follows overcrowding with mathematical precision."