THE PHYSIOLOGY OF THE AVIATOR 107 



more than ordinary activity, and the carbonic acid of the 

 blood is thus reduced below the normal amount, a com- 

 pensatory fall of the alkaline reserve occurs. The body 

 is evidently endowed with the ability to keep the ratio 

 of H 2 CO 3 to NaHCO 3 normal, not only by eliminating- 

 CO 2 when the alkali is neutralized, but also by the passage 

 of sodium out of the blood into the tissue fluid (or by 

 some equivalent process) to reduce the alkaline reserve. 

 A loss of CO 2 during over-active breathing is thus bal- 

 anced. If it were not balanced a state of alkalosis would 

 occur, which would inhibit and induce a fatal apnoea. 



It is really in this way I believe that some of those con- 

 ditions arise which nowadays are called "acidosis." If 

 so they are not truly acidosis, or rather the process pro- 

 ducing them is not acidosis, although the resultant con- 

 dition gives some of the most characteristic tests of this 

 condition. It is on the contrary a state, or rather a 

 process, which Mosso was the first to recognize, although 

 obscurely, and which he termed "acapnia" an excessive 

 elimination of CO 2 . Recent papers 7 from my laboratory 

 have shown that a sudden and acute acapnia induces pro- 

 found functional disturbances, including circulatory fail- 

 ure. 



It is one of the well-known facts in physiology that 

 deficiency of oxygen, or anoxemia, causes an "acidosis/' 

 Recent and as yet unpublished work of Dr. Haggard and 

 myself indicates that the process involved is almost dia- 

 metrically the opposite of that which has heretofore been 

 supposed to occur, and that the result is not a true acido- 

 sis. Under low oxygen, instead of the blood becoming- 

 at first more acid with a compensatory blowing off of 

 CO 2 , what actually occurs is that, as the first step, the 

 anoxemia induces excessive breathing. This lowers the 

 CO 2 of the blood, rendering it abnormally alkaline; and 



7 Henderson and Harvey, Amer. Jour. Physiol., 1918, 46, p. 

 533, and Henderson, Prince and Haggard, Jour. Pharmac. Ex- 

 per. Therap., 1918, 11, p. 189. 



