3 6 



FOOD AND DIGESTION 



enzymes known as trypsin, amylopsin, and steapsin, whose actions are, respect- 

 ively, proteolytic, amylolytic, and lipolytic (fat-splitting). Maltase, which 

 inverts the disaccharides, is also present, and a rennin is found in the pan- 

 creatic juice. 



CHEMICAL COMPOSITION OF PANCREATIC JUICE. (C. SCHMIDT.) 



An extract of pancreas made from the gland which has been removed 

 from an animal killed during digestion possesses the active properties of 

 pancreatic secretion. It is made by first dehydrating in absolute alcohol 

 the gland which has been cut up into small pieces. After the entire removal 

 of the alcohol the gland is pulverized and extracted in strong glycerin. 

 The amount of the ferment greatly increases if the gland be exposed to the 

 air for three or four hours before placing in alcohol; indeed, a glycerin 

 extract made from the gland immediately upon the removal from the body 

 often appears to contain none of the ferments. The conversion of zymogen 

 in the gland into the ferment takes place only after the gland stands a while. 

 Dilute acid assists or accelerates the conversion, and if a recent pancreas be 

 rubbed up with dilute acid before dehydration, a glycerin extract made 

 afterward, even though the gland may have been only recently removed from 

 the body, is very active. 



Nervous Regulation of the Secretion of the Pancreas. Fibers from 

 the vagus and from the splanchnics are distributed to the pancreas. In 

 Pawlow's laboratory it has been found that stimulation of these nerves leads 

 to the increased secretion of the pancreas. Popielski, in studying the effects 

 of dilute hydrochloric acid solution in the duodenum, which resulted in a 

 marked increase of pancreatic secretion, explained the phenomenon as a 

 local nerve reflex. 



Doubt has been cast on the whole question of nervous control by the 

 recent discovery of the fact that acid (0.4 per cent, hydrochloric acid) in the 

 duodenum results in the production of a chemical substance, secretin, by the 



