ACIDOSIS 63 



fold the amount of acid that the blood can receive without fatal fall 

 in pH. 



The fact that the buffers of the cells and fluids outside of the blood 

 assist the blood in maintaining its acid-base balance was shown by Van 

 Slyke and Cullen (1917). They injected into the veins of a dog more 

 than enough dilute sulphuric acid to neutralize all the blood buffers, and 

 found that about five-sixths of the acid had been neutralized by alkali from 

 other sources, as the decrease in blood bicarbonate was equivalent to only 

 about one-sixth of the injected acid. It therefore appears that disturbances 

 in the acid-base balance of the blood are, at least when of considerable 

 magnitude, transmitted to the rest of the body, the buffers of which 

 assist, those of the blood in maintaining its neutrality. 



d. The Physiologically Available Alkali of the Bicarbonate and of the 

 Other Blood Buffers. Definition of Alkali Reserve. In order that a 

 buffer shall neutralize an acid (HC1 for example) without change in pH 

 it is necessary that the buffer acid HA, set free by the reaction 

 BA -f- HC1 = BC1 4- HA, shall be completely removed, and in addition 

 as much of the HA formerly present as may be necessary to keep the ratio 

 BA : HA at the original value. Of the blood's important buffers, plasma 

 protein, cell phosphates, hemoglobin, and bicarbonate, only the bicarbonate 

 has an acid (CO 2 ) which can be quickly removed. Under all circum- 

 stances, physiological and pathological, in which the respiratory apparatus 

 is not specifically affected, it appears that the CO 2 is so regulated that a 

 normal pH is maintained. This is accomplished even by the ill diabetic 

 or nephritic so efficiently that, until the BHCO 3 has been reduced by 

 invading acids to *4, and perhaps even % of its normal value, the H 2 CO 3 

 is reduced in the same proportion, and a normal pH is maintained. 



So long as the pH is kept constant in the above manner, all the changes 

 in buffer alkali are those of the bicarbonate. For at a constant pH the 

 ratio BA : HA remains constant for each buffer, and however much 

 depletion the BHCO 3 may suffer, the alkali salts of the other buffers are 

 quite unaffected (that this is true has been demonstrated experimentally 

 as well as theoretically). 



One liter of average human blood contains bicarbonate sufficient to 

 neutralize 0.022 equivalent of acid, or 22 c.c. of N/l acid, and this is 

 the maximum that it could neutralize without change in pH, even if 

 the CO 2 tension were reduced to zero. 



However, at the cost of a fall in pH, the alkali of the other buffers 

 can be drawn upon, and since the publication of Van Slyke and Cullen's 

 paper conditions have been observed (certain cardiac cases, Peters and 

 Barr(&), 1921; ether anesthesia, Van Slyke, Austin and Cullen, 1920) in 

 which the pH does fall below normal. From data already quoted it 

 appears that for a short time at least the pH may fall as low as 6.95, 

 although not lower, without fatal results. 



