iv DIGESTION IN THE INTESTINE 209 



Like saliva, the pancreatic juice does not convert the whole of 

 the starch into sugar, after it has passed through the intermediate 

 products of erythrodextrin and achrob'dextrin, but dextrin always 

 appears as one of the end-products, along with the sugar, which 

 mainly consists of maltose (von Mering and Musculus). Glycogen 

 undergoes the same conversion. Pancreatic juice also dissolves 

 cellulose and gum (Schmulewitsch) to a much larger extent in 

 herbivora than in man and in carnivora. 



This digestive action of the pancreatic juice on the poly- 

 saccharides, which reduces them, with absorption of water, to 

 smaller and more soluble molecules, that can be easily absorbed 

 and assimilated, is of great importance in frugiverous birds, for 

 if the pancreatic secretion is drawn off externally, by a fistula, in 

 pigeons they die of progressive emaciation after a short time if 

 sugar be not administered, the giving of which delays their fate 

 (Langendorff). 



Little is known of the origin of the zymogen of amylopsin, and 

 the factors which convert it into the enzyme. According to some 

 authors, the centro-acinar cells elaborate the zymogen, and the 

 epithelium of the ducts pours out a kinase by which it is activated. 



Both entero-kinase and bile undoubtedly increase the arnyloly tic 

 activity of the pancreatic juice (Pawlow). This action comes off 

 also in a slightly acid medium, which is very favourable to the 

 digestion of carbohydrates ; in fact, we have seen that the greater 

 part of the intestine presents an acid medium. According to 

 Griitzner, weak acids, as also 0*7 per cent sodium chloride, increase 

 the action of the arnyloly tic enzyme, while more concentrated 

 solutions inhibit it, as do also alkaline salts, sulphates, alcohols, 

 chloroform, ether, thymol, etc. 



After a few hours in the thermostat at 37 C. pancreatic juice 

 loses its amylolytic activity (also its other enzymic properties, the 

 lipolytic first, and the proteolytic more slowly). 



The lipolytic action of pancreatic juice (due to steapsiri) is 

 exercised on the neutral fats, which are first emulsified per- 

 manently and completely, and then decomposed into glycerol and 

 fatty acids, with absorption of water. The power of emulsifying 

 fats is common to all alkaline fluids, but in a less perfect and less 

 stable degree, according to the quantity of free fatty acids which 

 Hoffmann finds to be present in all the fats. Alkali, in presence 

 of fatty acid, combines with it to form soap, which as Briicke 

 demonstrated, has the power of penetrating into neutral fat and 

 dividing it up into minute drops separated by a thin film of soap. 



In order to prove that pancreatic juice really has the property 

 of decomposing neutral fats, they must first be freed from the 

 fatty acids which they contain by dissolving them in ether and 

 shaking, after which the ethereal layer is separated and slowly 

 evaporated, leaving a residue of perfectly neutral fat, which on 

 VOL. ii p 



