70 PHYSIOLOGY OF ALIMENTATION. 



of maltose and dextrin. Caseinase is the name given to 

 the milk-curdling ferment of the pancreas. It is similar 

 to the milk-curdling ferment of the stomach. Lactase is 

 present in the pancreas only at certain periods in the life 

 of an animal and under certain conditions. It is found 

 normally in the pancreatic secretions of the puppy during 

 the period of lactation. In adult dogs it is absent, but it 

 can be made to appear again if the dog is kept for some 

 time on a milk diet or any diet containing milk-sugar. This 

 ferment has the power of acting upon milk-sugar (lactose) 

 and converting it into dextrose and galactose. A detailed 

 discussion of these ferments is given further on. 1 



It is as yet not entirely settled whether the ferments are 

 secreted as such from the pancreas or as preferments. Ac- 

 cording to DELEZENNE, FROUIN, and PopiELSKi, 2 the juice as 

 collected directly from the pancreatic duct never contains 

 alkali-pro teinase (trypsin), but only its preferment (tryp- 

 sinogen). This yields alkali-proteinase, however, as soon as 

 it flows over the mucous membrane of the duodenum, where 

 it encounters enterokinase. 3 Whether similar conditions hold 

 for the other ferments is a matter of dispute. 



In human pancreatic juice GLAESSNER could find no alkali- 

 pro teinase (trypsin), but only the proferment, which could, 

 however, be converted into alkali-proteinase by adding to 

 it an extract (enteTokinase) of the mucous membrane of the 

 small intestine obtained from human corpses. Both lipase 

 and amylase were also found, but no maltase, sucrase, or 

 lactase, a fact which agrees well with experimental findings 

 in animals. 



4. The Bile is the name given to the secretion from the 

 liver which is poured into the duodenum through the com- 



1 See Chapters IV, V, VI, VII, and VIII. 



2 DELEZENNE and FROUIN. Comptes rendus de Pacad., CXXX1V, p. 

 1526; Comptes rendus de Soc. biol., L1V, p. 691; POPIELSKI. Central- 

 blatt fur Physiologic, XVII, p. 65. 



3 See Chapter XIII, Part 4. 



