346 HUMAN PHYSIOLOGY 



pigment is the result of the decomposition of haemoglobin 

 and the acids are the result of proteid disintegration. 



All these facts seem to indicate that bile is the medium 

 by which the waste products of hepatic metabolism are 

 eliminated, just as the waste products of the body generally 

 are eliminated by the kidneys. 



B. 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 second the duct is made to open on the surface 

 of the abdomen. 



1. Characters and Composition. When obtained from a 

 temporary fistula, immediately after the operation, the pan- 

 creatic juice is a clear, slimy fluid, with a specific gravity 

 often of 1030 and an alkaline reaction. It contains an 

 abundance of a native proteid having the characters of a 

 globulin, and the alkalinity is probably due to carbonate 

 and alkaline phosphate of soda. From a permanent fistula 

 a more abundant flow of more watery secretion may be 

 collected. 



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

 cipitated by alcohol along with them, are the enzymes upon 

 which the action of the pancreatic juice depends. They are 

 three in number. (Chemical Physiolgy, p. 20.) 



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

 alkaline or neutral fluid, converts native proteids into 

 peptones, and is capable of still further breaking up these 

 peptones into simpler non-proteid bodies. It does not cause 

 solid proteids to swell up but simply erodes them away. 



The pancreatic juice brings about this breaking down in 

 stages. Fibrin and similar bodies first pass into the condi- 

 tion of soluble native proteids and then into deutero-proteose, 

 while boiled egg white appears at once to yield deutero-pro- 

 teose. The deutero-proteose is then changed into peptone, 

 and part of that peptone may split up still further into a 



