476 DIGESTION. 



parallelism exists in the two enzyme actions with extracts of the dog's 

 and calf's, stomach, and, also on testing the two enzyme actions upon the 

 same casein solution no parallelism was present. The pathological cases 

 in man, if the observations are reliable, where only one enzyme action 

 occurs, seems to dispute the identity of the action of these two enzymes. 

 This opposition is also shown by the fact that pepsin, so far as known, 

 only has a digestive action in the presence of free H ions, while the 

 coagulation of milk occurs in the absence of these and indeed in the 

 presence of HO ions. Among other facts which contravene the identity 

 is the fact that a pepsin solution can be prepared which has a digestive 

 action but cannot coagulate milk, and the reverse, namely, rennet solu- 

 tions can be made which coagulate milk but do not have digestive action 

 in acid reaction (HAMMARSTEN 1 ). The observations of DuccEScm, 2 

 that pepsin but no rennin occurs in the stomach of the Didelphys, also 

 conflict with the identity of the two enzymes. 



The views of NENCKI and SIEBER S take a certain reconciliary posi- 

 tion. According to them pepsin forms a gigantic molecule which has 

 various side-chains, one of which has digestive action in acid solution 

 while the others coagulate milk. This view coincides well with most 

 of the observations made thus far. 



In regard to the formation of pla steins under the influence of rennin 

 solutions and other enzyme solutions, see Chapters I and II. 



Gastric Lipase (STOMACH STEAPSIN). F. VoLHARD 4 made the dis- 

 covery that the gastric juice has a strong fat-splitting action only when 

 the fat is in a fine emulsion, as in the yolk of the egg, in milk or in cream. 

 Considerable controversy has arisen in regard to the importance of the 

 splitting of fat, and the occurrence of a special gastric lipase is indeed 

 disputed. From numerous observations it follows without question 

 that in man and many animals a gastric lipase occurs and is secreted 

 with the gastric juice. Nevertheless the extent of fat splitting in the 

 stomach is generally not very grqat. In its action this lipase follows 

 SCHUTZ'S rule and in its other properties it seems to vary in different 

 animals. 



The question whether the cover cells, principally, or the chief cells 



1 Zeitschr. f. physiol. Chem., 56. 



2 Centralbl., f. Physiol. 22, 784. 



3 Zeitschr. f. physiol. Chem., 32. 



4 Volhard, Munch, med. Wochenschr., 1900, and Zeitschr. f. klin. Med., 42, 43. 

 See also Stade, Hofmeister's Beitrage, 3; A. Fromme, ibid., 7; A Zinsser, ibid.; H. 

 Engel., ibid.; and Inouye, Arch. f. Verdauungskrank., 9; Falloise, Arch, internat. d. 

 Physiol., 3 and 4; London, Zeitschr. f. physiol, Chem., 50; Levites, ibid., 49; Laqueur. 

 Hofmeister's Beitrage, 8, 281; Heinsheimer, Deutsch. med. Wochenschr., 32, and 

 Arbeiten aus d. pathol. Institute, Berlin (Hirschwald, 1906). 



