492 DIGESTION. 



fact has been substantiated by the observations of PASCHUTIN, BROWN 

 and HERON, BASTIANELLI, and TEBB. 1 A lactose-inverting enzyme, 

 a lactase, also occurs, as shown by ROHMANN and LAPPE, PAUTZ and 

 VOGEL, WEINLAND, and ORBAN, 2 in new-born infants and young ani- 

 mals, and also in grown mammals which were fed upon a milk diet (see 

 Chapter I, page 52). The lactase can be obtained more abundantly 

 from the mucosa than from the juice and according to some occurs only 

 in the cells. The claims as to the occurrence of a glucoside splitting 

 enzyme are disputed (FROUIN, OMI 3 ) . 



Besides erepsin and the other enzymes mentioned, the intestinal 

 mucosa also contains substances which have an inhibitory action upon 

 pepsin and trypsin. (DANILEWSKY and WEINLAND 4 ), also enterokinase 

 or a mother-substance of the same, and finally also the so-called pro- 

 secretin. These two last-mentioned bodies, which are closely connected 

 with the secretion of pancreatic juice, will be discussed in connection 

 with this digestive fluid. 



V.& The various enzymes are not formed in equal quantities in all parts 

 of the intestine. Diastase and invertase occur, according to BOLDY- 

 REFF, all through the intestine, while the lipase on the contrary does not 

 occur in the lower parts. The kinase occurs only in the upper part of 

 the intestine (BOLDYREFF, BAYLISS and STARLING, DELEZENNE). Ac- 

 cording to HEKMA the kinase occurs in all parts of the intestine, but 

 most abundantly in the duodenum and the upper part of the jejunum. 

 The enzymes, FALLOISE claims, generally occur in greatest abundance 

 in the upper parts of the intestine; but the erepsin occurs to a greater 

 extent in the jejunum than in the duodenum. According to the investi- 

 gations of VERNON the behavior of erepsin is not the same in different 

 animals. In cats and hedge-hogs the duodenum is richer in erepsin than 

 the jejunum and ileum; in rabbits it is the reverse, namely, the ileum 

 is much richer than the duodenum. The secretin, according to BAY- 

 LISS and STARLING, is formed entirely in the upper part of the intestine. 

 The epithelium-cells of the glands or the mucous membrane are generally 

 considered as the seat of formation of the enzymes, and the same is 

 true also for the enterokinase, according to BAYLISS and STARLING, 



^aschutin, Centralbl. f. d. med. Wissensch., 1870, 561; Brown and Heron, Annal. 

 d. Chem. u. Pharra., 204; Bastianelli, Moleschott's Untersuch, zur Naturlehre, 14 

 (this contains all the older literature). See also Miura, Zeitschr. f. Biologic, 32; Wid- 

 dicombe, Journ. of Physiol, 28; Tebb, ibid., 15. 



2 Rohmann and Lappe, Ber. d. deutsch, chem. Gessellch., 28; Pautz and Vogel, 

 Zeitschr. f. Biologic. 32; Weinland, ibid., 38; Orban, Maly's Jahresber., 29. 



3 Frouin and Thomas, Arch, internat. de Physiol., 7; Omi, Das Verhalten- des 

 Salizins im tierschen Organismus, Inaug.-Dissert. Breslau, 1907. 



4 See footnote 3, p. 486. 



