IQO TEXT-BOOK OF PHYSIOLOGY. 



it is large, practically all of the fat undergoing this decomposition, with 

 the formation of soap and glycerin prior to their absorption. 



According to Pawlow, the relative amounts of the pancreatic enzymes 

 produced, are conditioned by the character and amounts of the food principles 

 consumed. Thus, if chyme contains an excess of either starch, protein, or 

 fat, there is a corresponding increase in the amount of either amylopsin, 

 trypsin, or steapsin produced. The pancreas apparently adapts its activities 

 to the character of the food. Though it is probable that each enzyme is a 

 derivative of a special zymogen, it is positively known that this is the case 

 only with trypsin. This enzyme is a derivative of the zymogen, trypsinogen, 

 the production of which is thought to be the special function of secretin. 

 The pancreatic juice at the moment of its discharge into the intestine does 

 not contain trypsin but trypsinogen. The transformation of the latter into 

 the former is accomplished, according to Pawlow, by a special activating 

 ferment secreted by the epithelium of the small intestine and termed entero- 

 kinase. 



The rapidity with which pancreatic juice in the presence of bile and 

 hydrochloric acid (under conditions such as are present in the duodenum) 

 can develop sufficient fatty acid to form an emulsion was determined by 

 Rachford to be two minutes. The activity of steapsin is thus shown to be 

 very great. 



Physiologic Action of the Intestinal Juice. The part played 

 by the intestinal juice in the digestive process is yet a subject of discussion, 

 as the results obtained by different observers are in some respects con- 

 tradictory, due to the fact that animals, including human beings, have 

 been the subjects of experimentation. Notwithstanding the actions of 

 saliva, gastric and pancreatic juice, there yet remain in the food saccharose, 

 maltose, and lactose, three forms of sugar which are believed by most to 

 observers to be non-assimilable and therefore require some change before 

 they can be absorbed and assimilated. . An extract of the intestinal mucous 

 membrane or the intestinal juice of a dog, added to a solution of saccharose, 

 will in a very short time convert it into dextrose and levulose, which together 

 constitute invert sugar. The enzyme by which this inversion is produced, 

 though nothing definite is known as to its nature, has been termed invertase 

 or saccharase. Tubbey and Manning state that the human intestinal juice 

 as obtained by them has the same action. In the case of intestinal fistulas 

 reported by Busch, which were supposed to be located in the upper third of 

 the intestine, it was found that when saccharose was introduced into the 

 lower opening, it was not inverted but appeared in the feces unchanged. 



Maltose is also rapidly transformed into dextrose. Lactose appears 

 to be unaffected by the pure juice. As it is non-assimilable it has been 

 supposed to undergo conversion into dextrose and galactose while passing 

 through the epithelial cells of the intestinal mucosa. In either case the 

 transformation is brought about by two ferments known respectively as 

 maltase and lactase. 



The intestinal juice also contains the two ferments enterokinase and 

 erepsin. The former activates the trypsinogen of the pancreatic juice and 

 converts it into trypsin; the latter acts on the peptones and reduces them to 

 peptids and amino-acids.. 



