390 THE COMPOSITION OF EXPIRED AIR. 



The chronic effects include the favoring of the action of certain 

 specific causes of disease commonty known as contagious, if these are 

 present, and perhaps also a general lowering of vitality. 



The statistical evidence collected by the English Barrack and Hos- 

 pital Commission (l) 1 as to the effects of insufficient ventilation upon 

 the health of soldiers in barracks, published in 18G1, showed that men 

 who live for a considerable portion of their time in badly ventilated 

 rooms have higher sickness and death rates than have those who 

 occupy well -ventilated rooms, other conditions being the same; and 

 this has also been found to be true with regard to monkeys and other 

 animals. It is evident, however, that in a room occupied by animals 

 or men there are many sources of impurity besides the exhaled breath, 

 and it is still a question whether the expired air contains substances 

 injurious to life, excluding carbonic acid. 



The widely divergent results obtained and conclusions reached by 

 different investigators during the last ten years as to whether the 

 exhaled breath of men and animals contains a peculiar volatile organic 

 poison, have made it desirable to repeat and vary such experiments in 

 order, if possible, to settle this important point. The chemical analyses 

 of the air of overcrowded rooms, and the experiments upon animals 

 with various proportions of carbonic acid, made by many investigators, 

 indicate that the evil effects observed are probably not due to the com- 

 paratively small proportions of carbonic acid found under such circum- 

 stances. 



Claude Bernard (2), in 1857, experimented with animals confined in 

 atmospheric air and in mixtures both richer and poorer in oxygen than 

 atmospheric air. A small bird placed in a bell glass of a little more 

 than 2 liters' capacity, containing a mixture of 13 per cent carbonic 

 acid, 39 per cent oxygen, and 48 per cent of nitrogen, died in two and 

 one-half hours. He demonstrated that carbonic acid is not poisonous 

 when injected under the skin of animals — as much as one liter injected 

 under the skin of a rabbit producing no ill effects. No ill effects fol- 

 lowed the injection of the gas into the jugular vein and into the carotid 

 artery. An atmosphere of equal parts of oxygen and nitrogen had no 

 effect upon an animal confined in it, while an atmosphere composed of 

 equal parts of carbonic acid and of oxygen produced immediate death 

 in the animal placed in it. He explains the poisonous effects of car- 

 bonic acid when respired to be due to the fact that it deprives the 

 animal of oxygen. Similar results were reported by Valentin (3) and 

 by Paul Bert (4). 



Richardson, in 1860-61 (5), found that a temperature much higher 

 or lower than 20° C. had the effect of shortening very considerably the 

 lives of animals confined in an unventilated jar, and that these effects 

 were more marked when the animals were confined in an atmosphere 



'The numbers in parentheses refer to the bibliographical list appended to this 

 report. 



