320 VETERINARY PHYSIOLOGY 



stitched to the abdominal opening. For experiments on pan- 

 creatic digestion extracts of the pancreas are generally used. 



1. Characters and Composition. — When obtained immedi- 

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

 slimy fluid, with a specific gravity of about 1015 and an 

 alkaline reaction. It contains an abundance of a native 

 protein having the characters of a globulin, and its alkalinity 

 is probably due to sodium carbonate and disodium phosphate. 

 From a permanent fistula a more abundant flow of a more 

 watery secretion may be collected. 



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

 cipitated along with it by alcohol, are the enzymes, upon 

 which the action of the pancreatic juice depends {Chemical 



Physiology). 



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

 alkaUne 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 

 proteins in stages. It does not cause sohd 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 deiUero-proteose. The deutero-proteose is then 

 changed into pjeptone, and part of that peptone is split into 

 a series of bodies which no longer give the biuret test. 

 These consist chiefly of the component polypeptides, am,ino- 

 rtcicfe, and of ammonm compounds (see p. 18). 



Amino-propionic acid linked to indol — tryptophan — is 

 also split off, and, if chlorine water is added to a pancreatic 

 digest which has proceeded for a long time, this gives a rose- 

 red colour. 



On nucleo-proteins, trypsin acts by digesting the protein 

 and dissolving the nucleic acid so that it may be absorbed. 



On collagen and elastin trypsin has httle action ; but on 

 gelatin it acts as upon proteins. 



2nd. A Diastase or Amylolytic Enzyme. — This acts in 

 the same way as ptyalin, but more powerfully, converting a 



