206 RESPIRATION 



does not appear to me that anything which has recently been 

 published, points to any important modification of the conclu- 

 sions embodied in this chapter. In view of the great confusion 

 which evidently exists as to the subject, it may, nevertheless, be 

 useful to indicate more explicitly the reasons for regarding the 

 words "acidosis" and "alkalosis" as denoting deviations towards 

 the acid or alkaline side respectively of the normal reaction or 

 hydrogen-ion concentration within the body. 



Acidosis and alkalosis are now frequently regarded as condi- 

 tions in which, whether or not there is an alteration in actual 

 reaction, the "alkaline reserve" of the blood plasma is diminished 

 or increased. This definition originated in a paper by Van Slyke 

 and Cullen in which they pointed out the ease with which varia- 

 tions in the "alkaline reserve," or total capacity of the blood 

 plasma for combining with CO 2 can be determined experimentally, 

 and the advantages of using oxalated blood plasma in place of 

 whole blood for the purpose. 56 Though they stated clearly that 

 variations in alkaline reserve are no direct measure of the varia- 

 tions in actual reaction of the blood, they, very unfortunately as 

 I think, proceeded to define "acidosis" as simply a condition in 

 which the alkaline reserve of the blood is diminished. It is, how- 

 ever, to variations in reaction, and not in the conveniently meas- 

 ured alkaline reserve of the plasma that the body is reacting 

 in conditions of acidosis or alkalosis; and to define acidosis or 

 alkalosis as anything else than a deviation towards the acid or 

 alkaline side of the normal reaction seems to me quite unjustifiable. 



The confusion has been added to by the general failure to 

 realize the extreme delicacy of physiological regulation of re- 

 action, as compared with the comparative roughness of our present 

 means of directly measuring changes in reaction. Thus in cases 

 where there are all the physiological signs of acidosis, the avail- 

 able means of direct measurement may show no sign of the 

 change; and hence it has been quite wrongly assumed that no 

 change exists. This has contributed towards an acceptance of the 

 definition of acidosis as a condition, not of increased hydrogen- 

 ion concentration. within the body, but of diminished alkaline re- 

 serve. The picturesque expression "alkaline reserve" is evidently 

 an unfortunate one in so far as it suggests a reserve of alkali not 

 in actual use. The alkali weakly combined in the body is in reality 

 always in physiological use, and the most urgent symptoms of 

 acidosis appear long before the alkaline reserve disappears. 



"Van Slyke and Cullen, Journ. of Biol. Chem., XXX, p. 289, 1917. 



