488 DIGESTION. 



refer the reader to what has been previously stated on this subject in 

 Chapter VIII, pages 385 and 386. 



V. THE CHEMICAL PROCESSES IN THE INTESTINE. 



The action which belongs to each digestive secretion may be essen- 

 tially changed under certain conditions by being mixed with other 

 digestive fluids for various reasons, and also by the action of the enzymes 

 upon each other; 1 and since the digestive fluids which flow into the 

 intestine are mixed with still another fluid, the bile, it will be readily 

 understood that the combined action of all these fluids in the intestine 

 makes the chemical processes going on therein very complicated. 



As the acid of the gastric juice acts destructively on ptyalin, this 

 enzyme has no further diastatic action, even after the acid of the gastric 

 juice has been neutralized in the intestine. ROGER and SIMON 2 claim 

 to have observed in saliva made inactive by the gastric juice, a reactiva- 

 tion caused by the pancreatic juice, but these investigations do not seem 

 to be fully conclusive. The bile has, at least in certain animals, a slight 

 diastatic action, which in itself can hardly be of any great importance, 

 but which shows that the bile has not a preventive, but rather a beneficial 

 influence on the energetic diastatic action of the pancreatic juice. MAR- 

 TIN, WILLIAMS, PAWLOW, and BRUNO 3 have observed a beneficial action 

 of the bile on the diastatic action of the pancreas infusion. To this 

 may be added that the organized ferments which habitually occur in the 

 intestine and sometimes in the food have partly a diastatic action and 

 partly produce a lactic-acid and butyric-acid fermentation. The maltose 

 which is formed from the starch seems to be converted into dextrose 

 in the intestine. Cane-sugar is inverted in the intestine, and, at least 

 in certain animals, also lactose. There does not seem to be any doubt 

 that cellulose, especially the fine and tender varieties, is in part dissolved 

 in the intestine. LOHRISCH 4 found that on an average of 50 per cent 

 of the introduced cellulose and hemicellulose was digested in human 

 beings and yielded the corresponding sugar. That cellulose undergoes 

 a fermentation in the intestine by the action of micro-organisms, produc- 

 ing marsh-gas, acetic acid, and butyric acid, has been especially shown 

 by TAPPEINER ; still it is not known to what extent the cellulose is destroyed 

 in this way. 5 



1 See Wroblewski and collaborators, Hofmeister's Beitrage, 1. 



2 Compt. rend. soc. biol., 62. 



3 Martin and Williams, Proceed, of Roy. Soc., 45 and 48; Bruno, footnote 2, 

 p. 479. 



4 Cited from Bioch. Centralbl., 8, 334. 



5 On the digestion of cellulose see Henneberg and Stohmann, Zeitschr. f. Biologic, 

 21, 613; v. Knieriem, ibid., 67; Hofmeister, Arch. f. wiss. u. prakt. Thierheilkunde, 



