General Conclusions 1037 



C. Diastases, poisons, and true viruses resist the action of oxygen 

 at high tension. 



D. The harmful effects of lowered pressure can be effectively- 

 prevented by breathing an air sufficiently rich in oxygen to main- 

 tain the tension of this gas at its normal value (20.9) . 



Those of increased pressure will be prevented by using air 

 sufficiently low in oxygen to secure the same result. 



E. In a general way, the benign or harmful gases (oxygen, car- 

 bonic acid, etc.) act on living beings only according to their ten- 

 sion in the surrounding atmosphere, a tension which is measured 

 by multiplying their percentage by the barometric pressure; the 

 increase of one of these factors can be compensated for by the 

 decrease of the other. 



F. When animals possess reservoirs of air either completely 

 closed (the swimming bladder of acanthopterygian fish, etc.), or 

 in communication with the air only during decompression (swim- 

 ming bladder of Cyprinidae, intestines of air-breathing vertebrates, 

 etc.) , or in communication with the air during compression as well 

 as decompression but by orifices that are too narrow (lungs of air- 

 breathing vertebrates, etc.) , the increase or decrease of pressure 

 may have physico-mechanical effects. 



G. Sudden decompression beginning with several atmospheres 

 has an effect (except for a few cases included in F) only by allow- 

 ing to return to the free state the nitrogen which had become dis- 

 solved in the blood and the tissues under the influence of this 

 pressure. 



H. The organisms at present existing in a natural state on the 

 surface of the earth are acclimated to the degree of oxygen tension 

 in which they live: any decrease, any increase seems to be harmful 

 to them when they are in a state of health. 



Therapeutics can advantageously use these modifications in dif- 

 ferent pathological conditions. 



I. The barometric pressure and the percentage of oxygen have 

 not always been the same on our globe. The tension of this gas 

 has probably been diminishing and no doubt will continue to 

 diminish. That is a factor which has not yet been taken into 

 account in biogenic speculation. 



Their power of reaction against these different modifications 

 leads us to suppose that microscopic organisms must have appeared 

 first and that they will disappear last, when life becomes extinct 

 through insufficiency of oxygen tension. 



