14 GASTRIC DIGESTION OF PROTEINS 



for clinical purposes, has been very much overestimated. 

 The actual facts may from a practical standpoint be stated 

 without hesitation as follows : The free hydrochloric acid of 

 the gastric juice in the presence of albuminous food is 

 quickly linked either completely or partly to the proteins or 

 their cleavage products. It should be kept in mind that 

 proteins are such weak bases that their salts are open 

 to extensive hydrolytic dissociation 32 so much so that in 

 dissolving them a part only of a given protein-salt remains 

 as such, the remainder reverting at once to protein and 

 free hydrochloric acid. The old belief was that the free 

 acid alone had any important bearing upon the digestion, 

 and it was for this reason that so much stress was laid upon 

 its estimation. 33 It was doubted, for example, because the 

 measurement of the concentration of hydrogen-ions in the 

 infant's stomach showed only very low tension, whether the 

 pepsin here could have as its chief function a digestive ac- 

 tivity or whether it would not much more likely act as a lab 

 ferment. 34 It seems important that, as Julius Schiita 

 demonstrated, the presence of H-ions is not absolutely 

 necessary for peptic digestion; the process begins at once 

 in the presence of no more than a very small amount of 

 combined acid (hydrochloric acid linked to albumin). 

 Schiitz believes that the principal purpose of the excessive 

 (i.e., "free") hydrochloric acid is probably to protect the 

 native proteins from loss of the hydrochloric acid linked to 

 them which the proteid catabolic products arising in the 

 course of digestion endeavor to abstract; that therefore it 

 is no more than a reserve stock. From this point of view 

 it is not the relative concentration but the absolute quantity 

 of free acid present which should stand as a measure of the 



33 Literature: O. Cohnheim, Nagel's Handb. d. Physiol., 2, 543-547, 1907. 

 "Cf. A. Miiller (I. Med. Clinic, Vienna), Deutsche Arch. f. klin. Med., 

 94, 27, 1908. 



84 H. Davidsohn, Zeitschr. f. Kinderheilk., 2, 420, 1911. 



