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 Recent and as yet unpublished work of Dr.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. 



