SCHOOL-ROOM VENTILATION. 535 



we inhale minute portions of each other's bodies, but it is true neverthe- 

 less. In diphtheria, scarlatina, small-pox, measles, etc., these epithelial 

 scales come off in vastly greater quantities than in health, carrying 

 with them, in greater or less virulence, the peculiar infection in the 

 body whence they have arisen. The greater their number and the 

 more favorable the nidus in which they become deposited, the more 

 likely they are to become transplanted as primary centers of infection. 

 Hence it is important to prevent their accumulatio7i, as the greater 

 their numbers the greater the probability of their successful trans- 

 plantation ; and as they float in the air they follow its currents, and 

 are thus removed by ventilation. Other sources of organic matters are 

 various and numerous, but, with the following exception, of little im- 

 portance in the present connection. 



The cutaneous surface and the lungs give out certain odors, sui 

 generis, which are designated " animal exhalations." It is to these 

 that the heavy, sickening smell noticed on first entering a crowded 

 room is due. Odors being volatile and exceedingly light, these ex- 

 halations rise to the highest portions of the room ; and, if not allowed 

 to escape, accumulate there, saturating the air from above downward, 

 and finally reaching the floor. Of all the noxious matters in the fouled 

 air of a poorly ventilated school or public building, these are at once 

 the most perceptible, the most offensive, and the most rapidly pros- 

 trating. They produce a sensation of stifling by their irritation of the 

 branches . of the pneumogastric nerve distributed to the lungs and 

 larynx, and nauseate, probably by reflex action, through branches of 

 the same nerve distributed to the stomach. A distinguished physi- 

 cian, w^riting of an infant nursery under his charge where the chil- 

 dren did not thrive, and many died of diseases of the digestive or- 

 gans, says : " One remarkable circumstance observed was that there 

 was a faint odor always present in the room. Yet it was a large room, 

 about fifty feet in length. One side of the room was made up of win- 

 dows which went up about ten feet where the roof or ceiling beveled 

 up in an inverted A shape, which raised the room in the center seven 

 or eight feet more. Do what I would, I could not get rid of this smell. 

 One day, being much annoyed thereat, I procured some long steps 

 which extended about three feet above the upper ledge of the windows. 

 On walking up, no sooner had I got my head one foot above their 

 level, than I found a terrible odor that made me feel giddy and sick ; 

 and I was glad enough to come down. I instantly sent for a work- 

 man, and desired him to remove three or four tiles at each end of the 

 room, on a level with the highest point of the roof. He did so. In ten 

 minutes all odor had disappeared ; but his work was no sooner ended 

 than he was taken very giddy and practically sick, so completely 

 had he been overcome by the pestilential atmosphere." This incident 

 will again be referred to in speaking of ventilators. 



In regard to the moisture of the air, the following may be said : 



