EXPIRED AIR AND VENTILATION. 583^ 



EXPIRED AIR AND PROBLEMS OF VENTILATION. 



THE following are substantially the conclusions reached by 

 Drs. J. S. Billings, S. Weir Mitchell, and D. H. Bergey re- 

 garding the composition of expired air and its effects upon animal 

 life, which are published in the Smithsonian Contributions. 

 These contradictions of certain accepted views are important and 

 likely to give rise to discussion. 



There is no peculiar organic matter which is poisonous to 

 animals (excluding man) in the air expired by healthy mice, spar- 

 rows, rabbits, guinea-pigs, or men. The injiirious effects of such 

 air appeared to be due entirely to the diminution of oxygen or the 

 increase of carbonic acid, or to a combination of these two fac- 

 tors. It is very improbable that the minute quantity of organic 

 matter contained in the air expired from human lungs has any 

 deleterious influence upon men who inhale it in ordinary rooms. 

 In ordinary quiet respiration no bacteria are contained in the 

 expired air. In the act of coughing or sneezing such organisms 

 may be thrown out. The minute quantity of ammonia, or of com- 

 bined 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. The air in an inhabited room, 

 such as a hospital ward, in which experiments were made, is con- 

 taminated from many sources besides the expired air of the occu- 

 pants, and the most important of these contaminations are in the 

 form of minute particles or dusts. The experiments on the air of 

 the hospital ward showed that in this dust there were micro-or- 

 ganisms, including some of the bacteria which produce inflamma- 

 tion and suppuration, and it is probable that these were the only 

 really dangerous elements in this air. The results of experi- 

 ments, in which animals were compelled to breathe air vitiated 

 by the products of either their own respiration or by those of 

 other animals, make it improbable that there is any peculiar vol- 

 atile poisonous matter in the air expired by healthy men and ani- 

 mals other than carbonic acid. The effects of reduction of oxygen 

 and increase of carbonic acid, to a certain degree, appear to 

 be the same in artificial mixtures of these gases as in air in 

 which the change in their proportions has been produced 

 by respiration. An excessively high or low temperature has a 

 decided effect upon the production of asphyxia by diminution of 

 oxygen and increase of carbonic acid. At high temperatures the 

 respiratory centers are affected, where evaporation from the 

 skin and mucous surfaces is checked by the air being saturated 

 with moisture ; at low temperatures the consumption of oxygen 



