250 SCIENCE PROGRESS. 



Man ----- 38*5 per cent. 



Mice ----- 23-2 „ 



Dogs - - - - - 2i - o „ 



Rabbits ----- 27*6 ,, 



Small birds - 44*6 ,, 



We further found that by increasing or diminishing the 

 oxygen percentage of the air a proportional increase or 

 diminution was caused in the oxygen tension of the blood, 

 but that when a condition was produced in which the animal 

 began to show symptoms of suffering from want of oxygen 

 the proportional difference between the oxygen tensions in 

 the blood and in the alveolar air increased very markedly, 

 indicating apparently that want of oxygen stimulates the 

 epithelium to increased absorptive activity. 



On the theory that the lung epithelium plays an active 

 part in the absorption of oxygen it would be expected that 

 if by any means the epithelium could be thrown out of action 

 the laws of diffusion would then come into play alone, and 

 the oxygen tension of the blood leaving the lungs would 

 then fall to that of the alveolar air, or lower. During the 

 course of our experiments we found that a fall of body tem- 

 perature (which greatly diminishes the activity of all the 

 tissues) causes the oxygen tension in the arterial blood to 

 fall to about alveolar oxygen tension. Lorrain Smith has 

 since found that a similar effect follows a rise of body tem- 

 perature, in spite of the increased ventilation of the lungs ; 

 also that during the very acute infective process brought 

 about in mice by inoculation with a culture of baccillus 

 pyocyaneus a similar fall occurs. He has also succeeded in 

 producing the same fall in arterial oxygen tension by ex- 

 posing animals for a short time to oxygen at high pressure 

 and afterwards replacing them in air. Paul Bert has shown 

 that oxygen at high pressure is destructive to both animal 

 and vegetable life. Hence the fact discovered by Lorrain 

 Smith that it has a local effect on the lungs is in no way sur- 

 prising. If the exposure is sufficiently long a condition of 

 acute pneumonia is brought about, which causes the death 

 of the animal. A short exposure is, however, sufficient to 

 produce a condition in which the arterial oxygen tension 



