RESPIRATION 193 



ing in a leisurely manner a goal which is constantly receding from 

 them, so that it is a long time before they finally reach it. The 

 quantity of alkali which has to be removed from the blood and 

 tissues is very large, as a simple calculation will show. 



With the compensation of the alkalosis there also comes com- 

 pensation of any secondary anoxaemia caused by the alkalosis as 

 a consequence of the Bohr effect discussed so fully in Chapters IV 

 and VI. Owing to the increased breathing the percentage satu- 

 ration of the arterial blood is (without any allowance for increased 

 oxygen secretion) as high as at first, while the oxygen pressure in 

 the systemic capillaries is higher (i.e., nearer normal) on account 

 of the decreased alkalosis. Cyanosis may be, however, quite as 

 marked as before. By the administration of acid the adaptation 

 to a lowered oxygenation of the arterial blood could doubtless 

 be hastened. 



The study of responses to the anoxaemia and alkalosis of high 

 altitudes is of great medical interest, since, as already explained 

 in the two preceding chapters, anoxaemia is a very common and 

 often extremely dangerous clinical condition. There can be no 

 doubt that the same responses as occur in healthy persons at 

 high altitudes occur also in patients suffering from anoxaemia. It 

 is therefore important not to misunderstand these responses. 

 During the war, for instance, the intensely dangerous anoxaemia 

 of acute gas poisoning and ''shock" was sometimes treated by the 

 administration of alkalies, on the theory, based on nothing but the 

 unintelligent use of a new method of blood examination, that the 

 patients were suffering from "acidosis." Physiological knowledge 

 as to the deadly significance of serious anoxaemia, and the (sup- 

 posed) acidosis as an adaptive change tending towards its com- 

 pensation, was ignored. It is also important to understand that the 

 adaptive changes require time, and that so-called palliative treat- 

 ment, by giving this time, may in reality be curative. 



Another cause of interference with the lung regulation of blood 

 reaction is to place an animal or man in an atmosphere in which 

 the percentage or pressure of CO2 is so high that the regulation 

 breaks down completely and there is in consequence an excessive 

 and lasting fall in the Ph of the blood. This condition was studied 

 recently in animals by Yandell Henderson and Haggard.*^ They 

 made the very important and significant discovery that the acido- 

 sis thus produced gradually brings about a marked increase in the 



*" Yandell Henderson and Haggard, Journ. of Biol. Chem., XXXIII, p. 333, 

 1918. 



