452 DIGESTION. 



DuccHESCHi, 1 that pepsin but no chymosin occurs in the stomach of the 

 Didelphys, also conflict with the identity of the two enzymes. 



The views of NENCKT and SiEBER 2 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 preparation of chymosin solutions free from pepsin 

 and of pepsin solution free from chymosin see the work of HAMMARSTEN. 3 



Plastein. As mentioned on page 134, D ANILE WSKY first showed the 

 power of rennin solutions to cause a partial coagulation of proteoses 

 and of converting them into so-called plastein. It is unknown whether 

 this action is due to pepsin, chymosin or to another enzyme. 



Gastric Lipase (STOMACH STEAPSIN) . F. VOLHARD 4 made the discovery 

 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 great. 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 also, 

 or both, take part in the formation of free acid is disputed. 5 There can 

 be no doubt that the hydrochloric acid of the gastric juice originates 

 in the chlorides of the blood, because, as is well known, a secietion 

 of perfectly typical gastric juice takes place in the stomachs of fasting 

 animals or those which have starved for some time. As the chlorides 

 of the blood are derived from the food, it is easily understood, as shown 

 by CAHN, 6 that in dogs after a sufficiently long common-salt starvation 



1 Centrabl. f . Physiol., 22, 784. 



2 Zeitschr. f. physiol. Chem., 32. 



3 Zeitschr. f . physiol. Chem., 56. 



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). 



5 See Heidenhain, Pfliiger's Arch., 18 and 19, and Hermann's Handbuch, 5, part I, 

 " Absonderungsvorgange " ; Klemensiewicz, Wien. Sitzungsber., 71; Friinkel, Pfliiger's 

 Arch., 48 and 50; Contejean, I.e.; Kranenburg, Archives Teyler, Ser. II, Haarlem, 

 1901, and Mo. se,. Centralbl. f. Physiol., 17, 217. 



8 Zeitschr. f . physiol. Chem., 10. 



