226 PRACTICAL PHYSIOLOGY 



the spores become transformed into the active organisms which multiply 

 quickly, meanwhile receiving their nourishment from the half-digested 

 food-stuffs, which become partially decomposed as a consequence. 

 Among the products of this bacterial growth are several organic acids, so 

 that the food, before it has gone far along the intestine, again becomes 

 acid in reaction. The mucosa of the large intestine does not secrete 

 any digestive juices, its sole function being one of absorption. In its 

 passage along it the fluid of the intestinal contents becomes gradually 

 absorbed, and the unabsorbed residue forms the faeces. 



It will be seen, therefore, that there are four distinct digestive agencies 

 at work in the intestine, and we will now study the action of each of 

 these separately. 



The Pancreatic Juice. Composition This can be collected by pro- 

 ducing a fistula of the pancreatic duct. The juice is strongly alkaline 

 in reaction, gives a coagulum of proteid on boiling, and contains, besides 

 this, a considerable amount of organic matter. 



Its percentage composition varies very much with the method adopted 

 for collecting it, that obtained immediately after the establishment of 

 the fistula being very much richer in solids than that secreted a few 

 days later. 



In studying its digestive action we employ, as in the case of gastric 

 digestion, an extract of the gland. This extract may be made with 

 glycerine, after treating the minced gland with weak acid, or allowing 

 it to stand some time, so as to convert the zymogens into the active 

 ferments. Glycerine does not extract all the ferments, however, so 

 that it is more usual to employ the minced gland itself, or a watery 

 extract of it. 



The result of the investigations has shown that there are four 

 active ferments, one proteolytic trypsin ; one amylolytic amylopsin ; 

 one steatolytic steapsin; and one coagulative a milk curdling 

 ferment. 



I. Trypsin. Like pepsin this hydrolyses proteid, and leads to the 

 production of proteoses and peptones. In this case, however, digestion 

 does not stop here, but the hemipeptone is further hydrolysed, amido 

 acids and hexone bases resulting ; the ultimate decomposition products 

 are, in fact, almost the same as when a strong acid is used as the 

 hydrolysing agency (see Proteids, p. 170). 



