THE COMPOSITION OF EXPIRED AIR. 407 



animal, on the amount of fresh air supplied, on conditions of tempera- 

 ture and moisture, and on individual peculiarities of the animal; and 

 it seems probable that variations in these factors will account for the 

 different results obtained by different experimenters. The symptoms 

 in the animals which died were those of death by slow asphyxia. 



Microscopic examination of the organs presented a picture coinciding 

 with the gross post-mortem appearances. In the lungs the capillaries 

 were found to be distended with blood, occluding in many cases the 

 lumen of the alveoli and air cells, and presenting a typical picture of 

 passive hyperemia. In the liver, kidneys, and spleen, as well as in the 

 intestines, the capillaries were likewise overloaded with blood. Patho- 

 logical changes were but rarely noted, and some of these, such as slight 

 proliferation of connective-tissue elements between the tubules of the 

 kidney, and in rarer instances, in the interlobular spaces of the liver, 

 are such as are occasionally found in animals which have not been sub- 

 jected to such conditions, and may, therefore, have existed in the ani- 

 mals at the beginning of the experiment. All the changes which were 

 constantly present may properly be attributed to the action of the car- 

 bonic acid and the low percentage of oxygen in the atmosphere, inter 

 fering with the circulation and aeration of the blood. The lesions 

 reported by Brown-Sequard and d'Arsonval as characteristic in such 

 cases were not seen. No focal necroses or peculiar uniform degenera- 

 tive changes were found. The results of these experiments, therefore, 

 do not agree with those reported by Brown-Sequard and d'Arsonval — 

 and furnish no evidence of the existence of an organic poison in the air 

 expired by animals. 



CONCLUSIONS. 



1. The results obtained in this research indicate that in air expired 

 by healthy mice, sparrows, rabbits, guinea pigs, or men, there is no 

 peculiar organic matter which is poisonous to the animals mentioned 

 (excluding man), or which tends to produce in these animals any spe- 

 cial form of disease. The injurious effects of such air observed appeared 

 to be due entirely to the diminution of oxygen, or the increase of car- 

 bonic acid, or to a combination of these two factors. They also make 

 it very improbable that the minute quantity of organic matter con- 

 tained in the air expired from human lungs has any deleterious influence 

 upon men who inhale it in ordinary rooms, and, hence, it is probably 

 unnecessary to take this factor into account in providing for the ven- 

 tilation of such rooms. 



2. In ordinary, quiet respiration, no bacteria, epithelial scales, or 

 particles of dead tissue are contained in the expired air. In the act of 

 coughing or sneezing, such organisms 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 



