ACIDOSIS 57 



drafts upon their alkali the buffer salts have been so far reduced, and 

 the free buffer acids so far increased, that an unendurably low pll results, 

 death from acid intoxication follows. 



We shall now discuss in some detail the above four parts of the mechan- 

 ism whereby the body minimizes reaction changes resulting from acid 

 invasion, and restores its acid-base balance to normality after such dis- 

 turbances have occurred. 



1. The Neutralization of Acid by Buffers. The buffers are the direct 

 defenders of neutrality by which invading acids are first met, and they 

 are also involved in the subsequent restoration of normal reaction by 

 respiratory regulation of the CO 2 tension, and by renal excretion of other 

 acids. Their position in neutrality regulation is so central that unless their 

 mode of action is clearly y seen the whole combined physiological and 

 chemical mechanism for neutrality maintenance escapes one's grasp. We 

 shall therefore discuss the buffers, both as to their general nature and 

 their specific behavior in the blood. 



a. The Nature of Buffers. Buffers are salts of either weak bases or 

 weak acids, and are characterized by their ability to enable solutions in 

 which they are present to receive additions of limited amounts of either 

 acid or alkali with much less change of pH than would be caused by the 

 same additions to water, or to a solution containing only salts, such as 

 NaCl, that have no buffer power. All the important buffers of the blood, 

 viz., the bicarbonates, phosphates, and the alkali salts of the proteins, are 

 salts of weak acids. Of each buffer, part is present as free acid, part as 

 the salt of a strong base, and the pH of the blood is determined by the 

 relative proportions of buffer salts and free buffer acids respectively. 



The alkali salts which constitute the buffers of the blood are in effect 

 reservoirs of alkali, a portion of which they give up to neutralize car- 

 bonic or any other acid that enters the blood. In this manner act the 

 phosphates, and also the alkali salts of the plasma proteins and of the 

 hemoglobin. 



In regard to such buffers two general laws may be stated, the prin- 

 ciples underlying both of which may be found in L. J. Henderson's (a) 

 monograph on the regulation of body neutrality (1909). 



1. The hydrogen ion concentration of the buffer solution is propor- 



,. free acid HA _ n ,. *"*! 



tional to the ratio - or - - . Examples 01 such ratios in the 

 free salt BA 



H,CO 3 , BH,P0 4 , HHbO, HHb. > ' , . ,. 



bl d are - E * ^ t0 mdwate 



BH1 



monovalent base, such as Na or K, A to indicate the acid radical, BHbO 

 the alkali salt of oxyhemoglobin, HHbO the free oxyhemoglobin, BHb 

 and HHb the salt of reduced hemoglobin and the free protein respec- 

 tively.) 



