May 9, 1919] 



SCIENCE 



437 



tions on the inliabitants of towTis of closely 

 graded altitude from sea level up to that of 

 the highest inhabited place in our western 

 country. She has thus show-n that the mean 

 hemoglobin and the mean alveolar CO, of 

 the inhabitants of any town are functions 

 of the mean barometric pressure of the 

 place. 



I shall not discuss pulmonary oxygen se- 

 cretion now, because the problem is still 

 extremely obscure; nor the increased pro- 

 duction of red blood corpuscles, which is a 

 slow process requiring weeks for comple- 

 tion, and playing no considerable part in 

 the matter particularly before us. 



"We will tix our attention upon the fact 

 that both the alveolar COo of the pulmonary 

 air and the alkaline reserve of the blood are 

 reduced in accurate adjustment to any alti- 

 tude, or oxygen tension, to which a man is 

 subjected for a few days or even a few 

 hours. Tliis functional readjustment is, I 

 believe, of great significance in relation to 

 aviation, since it involves a larger volume 

 of breathing per unit mass CO^ eliminated : 

 it thus compensates in part for the rare- 

 faction of the air. 



But how is it brought about? And why 

 are the changes of breathing gradual, when 

 the changes of altitude and oxygen tension 

 are abrupt? The answer lies in part at 

 least in the mode of development, and the 

 nature of that acidosis of altitude to which 

 I have referred. It is scarcely necessary to 

 remind you that, as L. J. Henderson has 

 shown, the balance of acids and bases in the 

 blood, its Ch, depends upon the mainte- 

 nance of a certain ratio between the dis- 

 solved carbonic acid, HXO, and sodium 

 bicarbonate, NaHCOj, or as Van Slyke 

 terms it, the alkaline reserve. On the basis 

 of this conception the prevalent view of 

 acidosis is that, when acids other than car- 

 bonic are produced in the body, the bicar- 

 bonate is in part neutralized. The alkaline 



reserve is thus lowered, and the carbonic 

 acid of the blood being now in relative ex- 

 cess, an increased volume of breathing is 

 caused as an effort at compensation. 



Recent investigations' by Dr. H. W. Hag- 

 gard and myself show that an exactly oppo- 

 site process is likewise possible. "We find 

 that whenever respiration is excited to more 

 than ordinary activity, and the carbonic 

 acid of the blood is thus reduced below the 

 normal amount, a compensatory fall of the 

 alkaline reserve occurs. The body is evi- 

 dentlj' endowed with the ability to keep the 

 ratio of HoCOj to NaHCOa normal, not 

 only by eliminating CO^ 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, during 

 over-active breathing is thus balanced. If 

 it were not balanced a state of alkalosis 

 would occur, which would inhibit and in- 

 duce a fatal apnoea. 



It is really in this way I believe that 

 some of those conditions arise which nowa- 

 days are called "acidosis." If so they are 

 not truly acidosis, or rather the process 

 producing them is not acidosis, although 

 the resultant condition 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 recog- 

 nize, although obscurely, and which he 

 termed "acapnia" an excessive elimination 

 of C0„. Recent papers* from my labora- 

 tory liave shown that a sudden and acute 

 acapnia induces profound functional dis- 

 turbances, including circulatory failure. 



It is one of the well-known facts in physi- 



' Henderson and Haggard, Jour. Biol. Chem., 

 1918, 33, pp. 333, 345, 355, 365. 



8 Henderson and Harvey, Amer. Jour. Physiol., 

 1918, 46, p. 533, and Henderson, Prince and Hag- 

 gard, Jour. Pharmac. Exper. Therap., 1918, 11, p. 

 189. 



