482 



SCIENCE. 



[N. S. Vol. I. No. 18. 



matter contained in the air expired from 

 human lungs has any deleterious influence 

 upon men who inhale it in crowded rooms, 

 and hence it is probably unnecessary to take 

 this factor into accoimt in providing for the 

 ventilation of such rooms. 



2. In ordinary quiet respiration no bac- 

 teria, epithelial scales, or particles of dead 

 tissue are contained in the expired air. In- 

 the act of coughing or sneezing such organ- 

 isms or particles may probably be thrown 

 out. 



3. The minute quantity of ammonia, or 

 of combined nitrogen or other oxidizable 

 matters found in the condensed moisture of 

 human breath appears to be largely due to 

 products of the decomposition of organic 

 matter which is constantly going on in the 

 mouth and pharynx. This is shown by the 

 effects of cleansing the mouth and teeth 

 upon the amount of such matters in the 

 condensed moisture of the breath, and also 

 by the differences in this respect between 

 the air exhaled through a tracheal fistula 

 and that expired in the usual way. 



4. The air in an inhabited room, such as 

 the hospital ward in which experiments 

 were made, is contaminated from many 

 sources besides the expired air of the occii- 

 pants, and the most important of these con- 

 taminations are in the form of minute par- 

 ticles or dusts. The experiments on the air 

 of the hospital ward, and with the moisture 

 condensed therefrom, show that the greater 

 part of the ammonia in the air was con- 

 nected with dust particles which could be 

 removed by a filter. They also showed 

 that in this dust thei-e were microorganisms, 

 including some of the bacteria which pro- 

 duce inflammation and suppuration, and it is 

 probable that these were the only really 

 dangerous elements in this air. 



5. The experiments in which animals 

 were compelled to breathe an- vitiated hy 

 the produ^cts of either their own respii-ation 

 or by those of other animals, or M^ere in- 



jected with fluid condensed from expired 

 air, gave results contrary to tliose reported 

 by Hammond, by Brown-Sequard and d'Ai'- 

 sonval, and by Merkel ; but correspond- 

 ing to those reported by Dastre and Loye, 

 Russo Gilibert and Alessi, Hofinann AVel- 

 leuhof, Rauer, and other experimenters re- 

 ferred to in the preliminary historical 

 sketch of this report, and make it improb- 

 able that there is any peculiar volatile poi- 

 sonous matter in the air expired by healthy 

 men and animals, other than cai-bonic acid. 

 It must be borne in mind, however, that the 

 results of such experiments upon animals 

 as are referred to in this report may be ap- 

 plicable only in part to human beings. It 

 does not necessarily follow that a man 

 would not be injured by continuously liv- 

 ing in an atmosphere containing 2 parts 

 per 1,000 of carbonic acid and other prod- 

 ucts of respiration, of cutaneous excretion, 

 and of putrefactive decomposition of organic 

 matters, because it is found tliat a mouse, a 

 guinea pig, or a rabbit seems to suffer no 

 ill effects from living under such conditions 

 for several days, weeks or months, but it 

 does follow that the evidence which has 

 heretofore been supposed to demonstrate 

 the evil efl'ects of bad ventilation upon hu- 

 man health should be carefully scrutinized. 



6. The effects of reduction of oxygen and 

 increase of carbonic acid, to a certain de- 

 gree, appear to be the same in artificial 

 mixtures of these gases as in air in which 

 the change of proportion of these gases has 

 been produced by respiration. 



7. The effect of habit, which may enable 

 an animal to live in an atmosphere in which 

 by gradual change the proportion of oxy- 

 gen has become so low and that of carbonic 

 acid so high that a similar animal brought 

 from fresh air into it dies almost instantly, 

 has been observed before ; biit we are not 

 aware that a continuance of this immunity 

 produced by habit has been previously 

 noted. The experiments reported in the 



