26 THE COMPOSITION OF EXPIRED AIR, 



iufluence upon the increu-se ul' dist-a^t- and death-rates which statistical evidence has 

 shown to exist among persons livini; in crowded and uuveutihited rooms. The 

 Ueiioit of the Commissioners appointed to inquire into the reguhvtions affecting the 

 sanitary conditions of the British Army (1), properly lays great stress on the fact 

 that in civilians at soldiers' ages, in twenty-four large towns, the death-rate per 

 1000 was 11.9, while in the foot-guards it was 20.4, and in the infantry of the line 

 17.9, and showed that this difference was mainly due to diseases of the lungs 

 occurrini^ in soldiers in crowded and unventilated barracks. These observations 

 have since been repeatedly confirmed by statistics derived from other armies, from 

 lirisons, and from the death-i-ates of pei-sons engaged in different occupations, and, 

 in all cases, tubercular disease of the lungs and pneumonia are the diseases which 

 are most prevalent among persons living and working in unventilated rooms, 

 uidess such persons are of the Jewish race. But consumption and pneumonia are 

 caused by specific bacteria, wdiich, for the most part, gain access to the air-passages 

 by adhering to particles of dust which arc iidialed, and it is probable that the 

 greater liability to these diseases of persons living in crowded and unventilated 

 rooms, is, to a laige extent, due to the special liability of such rooms to become 

 infected with the germs of these diseases. It is, howevei-, by no means demon- 

 strated, as yet, that the only deleterious effect which the air of crowded barracks or 

 tenement-house rooms, or of foul courts and nan-ow streets, exerts upon the persons 

 who breathe it, is due to the greatei- number 'of pathogenic micro-oi'ganisms in such 

 localities. It is quite possible that such impure atmospheres may affect the vitality 

 and the bactericidal powers of the cells and fluids of the upper air-passages with 

 which they come in contact, and may thus predispose to infections, the potential 

 causes of which are almost everywhere present, and especially in the upper air- 

 passages and in the alimentary canal of even the healthiest persons, but of this we 

 have, as yet, no scientific evidence. It is very desiiable that researches should be 

 made on this point. 



X. The discomfoit produced by crowded, ill-ventilated rooms in persons not 

 accustomed to them is not due to the excess of carbonic acid, nor to bacteria, nor, 

 in most cases, to dusts of any kind. The two great causes of such discomfort, 

 though not the only ones, are excessive temperature and unpleasant odors. Such 

 rooms as those referred to ai-e generally overheated, the bodies of the occupants, 

 and, at night, the usual means of illumination, contributing to this result. 



The cause of the unpleasant, musty odor which is pei-ceptible to most persons 

 on passing from the outer air into a crowded, unventilated room is unknown; it 

 may, in part, be due to volatile products of decomposition contained in the expired 

 air of pei-sons having decayed teeth, foul mouths, or certain disorders of the diges- 



