196 RESPIRATION 



when the Ph of blood is altered, the alkaline reserve of the plasma 

 was distinctly diminished by forced breathing.^^ 



The blood reaction may, of course, be disturbed in other ways 

 than by interference with respiration. One of these ways is by 

 ingestion of acids or by production within the body of great ex- 

 cess of some organic acid. Walter's experiments, interpreted in 

 the light of our present knowledge, showed the effects of acid 

 poisoning in stimulating to the utmost all the means of diminishing 

 acidosis, including excessive breathing, greatly increased forma- 

 tion of ammonia, and secretion, presumably, of an abnormally 

 acid urine. The titration alkalinity or "alkaline reserve" of the 

 blood and doubtless also of the whole body was evidently dimin- 

 ished very greatly. 



Christiansen, Douglas, and Haldane produced a temporary true 

 acidosis by flooding the blood with lactic acid produced by mus- 

 cular anoxaemia during the heavy exertion of running several 

 times upstairs. In this case two results followed. In the first place 

 there was a fall in the resting alveolar CO2 pressure, which was, 

 in several experiments, about 39 mm. before the exertion, and 

 30.5 mm. about 10 minutes after the exertion. The blood absorbed 

 about 49 volumes of CO2 per 100 of blood before the exertion in 

 presence of the existing alveolar CO2 pressure, and only about 

 28 afterwards. After one and one-half hours both the resting 

 alveolar CO2 pressure and the absorbing power of the blood for 

 COo had returned to normal. 



In these experiments the capacity of the blood for absorbing 

 CO2 at a CO2 pressure of 40 mm. had been reduced by about 40 

 per cent, and the resting alveolar CO2 pressure by about 20 per 

 cent, corresponding to an increase of about 25 per cent in the 

 lung ventilation. There was thus a very distinct acidosis ; but ref- 

 erence to the calculations already made will show that the acidosis 

 could not have been detected by any existing method of directly 

 estimating hydrogen ion concentration. 



The great drop in the capacity of the blood for combining with 

 COo suggests at first that the blood had become correspondingly 

 inefficient as a carrier of CO2 from the tissues to the lungs, and 

 that this deficiency could only be made up by a greatly increased 

 circulation rate, if it was made up at all. The truth, however, is 

 that the main difference produced was that the dead weight of 

 CO2 always carried round by the blood was greatly diminished. 

 As a carrier of CO2 from the tissues to the lungs, the blood was 



*'^ Amer. Jotirn. of Physiol., LI, p. 568, 1920. 



