394 



SCIENCE 



[N. S. Vol. XXXVII. No. 950 



In the case of carbonic acid the equi- 

 librium is further complicated by the ac- 

 tivity of the lung in excreting the free acid 

 and regulating the concentration of that 

 svibstance, which is kept nearly constant. 

 Thus, when acid reacts with bicarbonate 

 in the body, it diminishes the latter sub- 

 stance without increasing the amount of 

 the acid. In this manner through the es- 

 cape of carbonic acid, the efficiency of the 

 equilibrium in the preservation of neutral- 

 ity is further greatly increased. Thus it is 

 that even in extreme acid intoxication, as 

 for instance diabetic coma, almost the only 

 chemical change that can be detected, as a 

 result of the action of enormous quantities 

 of acid through long periods of time, is a 

 large diminution in the bicarbonates of 

 the blood; in the instances above calcu- 

 lated this would amount to a decrease of 

 about 50 per cent, in the total carbonic 

 acid. Meantime about 20 per cent, of the 

 phosphoric acid of the body will probably 

 be changed from alkaline to acid phos- 

 phate, and the proteins will have given up 

 a portion of the alkali with which they are 

 combined. 



The recognition of the fact that diminu- 

 tion of bicarbonates is the principal effect 

 of acid intoxication upon the blood, in- 

 volves important consequences. On the 

 one hand it has become clear that the thera- 

 peutic use of sodium bicarbonate is desir- 

 able in a large variety of pathological con- 

 ditions and, on the other hand, it seems to 

 be certain that the evil effects of acidosis 

 largely depend upon interference with the 

 transport of carbonic acid and its excre- 

 tion from the body. In truth this equilib- 

 rium is intimately associated with the 

 respiratory function, and with a great 

 number of other fundamental physiological 

 activities, and with the osmotic pressure of 

 the cell. 



Further the profound influence of hy- 



drogen and hydroxyl ions upon many 

 enzymatic processes, and upon colloids in 

 general has been established, and it is grad- 

 ually becoming clear that all the physico- 

 chemical conditions in protoplasm — alka- 

 linity, osmotic pressure, colloidal swelling, 

 chemical equilibrium, temperature — are 

 interdependent, and that carbonic acid and 

 the acid-base equilibrium are among all 

 these things probably the most important 

 variables. 



The reason why it may be asserted that 

 carbonic and phosphoric acids and the pro- 

 teins are the only important substances 

 which are involved in the physiological 

 regulation of neutrality is that, for the 

 body as a whole, in the narrow range of 

 reaction which can actually occur, these 

 substances can neutralize about 30 liters of 

 0.1 N acid, and nothing else except other 

 substances of like ionization constants, in 

 equal concentration, even with the ad- 

 vantage of the escape of acid, can do as 

 much. 



It can not be too strongly emphasized 

 that this conclusion applies only to the 

 true aqueous solutions of the body. Of the 

 colloidal phase we have no knowledge, but 

 it is evident that they may act as reser- 

 voirs of supply and as vehicles of escape. 



It is also evident that, if enough acid be 

 produced locally, for instance, lactic acid 

 in the muscle, the protective mechanism 

 may be overthrown, and true acidity re- 

 sult. There is an important connection 

 between this consideration and theories of 

 fatigue and muscular contraction. 



But, as for the assertions themselves, 

 they rest upon one of the immutable prop- 

 erties of matter. Phosphoric and carbonic 

 acids in solution everywhere possess this 

 characteristic, independent of the presence 

 of everything else, just as they everywhere 

 possess their characteristic chemical com- 

 position. 



