Theories and Experiments 447 



above the proportions of the normal state up to the pressure of 773 

 thousandths; above this figure, the lungs exhale less carbonic acid 

 than before. 



And here is the rather vague explanation which they give for 

 this contradiction: 



At a low pressure, since the chemical effect dominates the me- 

 chanical influence, endosmosis finds in the conditions of pressure a 

 circumstance favorable to the development of the respiratory functions 

 without exosmosis being hampered by too strong a pressure .... and 

 therefore a growing increase in the exhalation of carbonic acid follows. 

 At a higher pressure the mechanical effect neutralizes and destroys 

 the chemical influence, to the point of preventing gaseous exosmosis 

 in the compressed air, without hindering the absorption of gases, 

 however. 



It is this storing of carbonic acid by the blood, under the in- 

 fluence of the compressed air, which would explain, according to 

 our authors, how: 



The baths of compressed air increase the exhalation of carbonic 

 acid outside the bath; this effect, which persists for several hours 

 after the treatment, is more perceptible two or three hours after- 

 wards than immediately after the bath. 



This would be owing to the fact that: 



The abnormal expansion of the pulmonary vesicles, as an effect 

 of a sufficiently strong pressure in compressed air, lessens the energy 

 and elasticity of the respiratory organs .... whereas, when after 

 the bath the mechanical influence suspends its action, the energy of 

 the lungs soon returns to its normal state, and by means of the gaseous 

 exosmosis which is no longer hampered, casts off in the form of 

 carbonic acid all the oxygen which it had absorbed in the bath under 

 the influence of endosmosis. 



Pravaz, 11 from whose book we have already quoted (page 415) , 

 after listing the favorable changes which the stay in compressed air 

 brings to the exercise of several important physiological functions, 

 finds that these considerable advantages have three causes of dif- 

 ferent types: 



A. The amplitude of the inspirations is increased for two 

 reasons: 



1. If it is certain that, under the ordinary conditions of life, the 

 inspiration is far from having the extent which the anatomical posi- 

 tion of the thoracic walls would permit, we cannot doubt that in a 

 great number of persons, and particularly in those who, because they 

 lead a sedentary life, need only a moderate encounter with the atmos- 

 phere for the purpose of hematosis, the retractility of tissue has 



