FOOD AND DIGESTION 361 



A. Pancreatic Secretion 



The secretion of the pancreas may, in the dog, be procured 

 by making either a temporary or a permanent fistula. In the 

 former case the duct is exposed, and a canula fastened in it; 

 in the latter the duct is made to open on the surface of the 

 abdomen, a small piece of the intestinal wall with the mucous 

 membrane round the opening of the duct being stitched to the 

 abdominal opening. 



1. Characters and Composition. When obtained immediately 

 from a temporary fistula, the pancreatic juice is a clear, slimy 

 fluid, with a specific gravity of 1030 or less and an alkaline 

 reaction. It contains an abundance of a native protein having 

 the characters of a globulin, and the alkalinity is probably 

 due to sodium carbonate and disodium phosphate. From a 

 permanent fistula a more abundant flow of more watery 

 secretion may be collected. 



2. Action. Closely associated with the protein, and pre- 

 cipitated by alcohol along with it, are the enzymes upon 

 which the action of the pancreatic juice depends. (Chemical 

 Physiology ) 



1st. A Proteolytic Enzyme Trypsin. This, in a weakly 

 alkaline or neutral fluid, converts native proteins into peptones, 

 and then breaks these peptones into simpler non-protein bodies. 



The pancreatic juice brings about this breaking down of protein 

 in stages. It does not cause solid proteins to swell up but simply 

 erodes them away. Fibrin and similar bodies first pass into the 

 condition of soluble native proteins and then into deutero-proteose, 

 while boiled egg white appears at once to yield deutero-proteose. 

 The deutero-proteose is then changed into peptone, and part of 

 that peptone is then split into a series of bodies which no longer 

 give the biuret test. These consist chiefly of the component 

 amido-acids of which the most important are leucin and 

 tyrosin, and of ammonia compounds (see p. 8). 



Amido-acetic acid linked to skatol tryptophane is also split 

 off, and if chlorine water is added to a pancreatic digestion, 

 which has proceeded for a long time, a rose-red colour is struck 

 (see p. 430). 



