204 DIGESTION 



with the emotions, for the intestinal movements are easily disturbed. 

 Other centers, actuating and inhibitory, probably are placed in the cord, 

 the spinal ganglia, or in the great abdominal plexuses. Despite all these 

 diverse facts, the probability is continually confirmed that the control 

 of the whole alimentary canal is of the simplest sort through the nerve- 

 net in its walls. Its neuro-muscular mechanism is doubtless a highly 

 unified structure, whose details remain, however, to be described. 



PANCREATIC JUICE is poured out, mixed with the bile, into the upper 

 portion of the duodenum; there it mixes with the intestinal juice proper, 

 forming altogether a very complex digestive liquid. The external secre- 

 tion of the pancreas is in different animals and at different times a 

 very variable substance. From a dog's temporary fistula its specific 

 gravity is about 1030; it is clear, but of a syrupy consistence, becoming 

 still more viscid on cooling; at 75 or at it coagulates. It is alkaline 

 in reaction, due probably to salts of sodium. It is rich in proteid. A 

 sample analyzed by C. Schmidt contained 900.8 parts water and 99.2 

 parts of solid material, of which 90.4 parts were organic matter and 8.8 

 parts ash. This ash was mostly sodium chloride, but contained also 

 sodium oxide, potassium chloride, trisodic phosphate, lime, magnesia, 

 earthy-phosphates, and iron. Its daily amount in man is perhaps 175 

 grams. 



Pancreatic juice contains probably at least five enzymes: trypsinogen, 

 hydrolyzing proteid; diastase (amylopsin), hydrolyzing carbohydrates; 

 lipase (steapsin), saponifying and indirectly emulsifying fats; probably 

 rennin, coagulating caseinogen ; and perhaps lactase and invertase. 



According to Bayliss and Starling, no trypsin is contained in fresh 

 pancreatic juice, but the trypsinogen there found is changed to trypsin 

 when it arrives in the intestine by the action of enterokinase (kinase), 

 secreted by the upper end of the gut. By means of erepsin from the intes- 

 tinal wall probably the peptone produced by hydrolysis is split still 

 farther into the amido-acids. 



Proteid. 



Albumoses. 

 Peptone. 



/ \ 



Mixture of many amido-acids having Tyrosin, tryptophan, cystin, alanin, 



complicated connections the substances amido-valerianic acid, leucin, aspara- 

 known as polypeptids. ginic acid, glutaminic acid, histidin, 



lysin, arginin. (Abderhalden.) 



Inasmuch as Lowi, and others after him, have been able to keep dogs 

 nourished by feeding them, for nitrogenous food, these amido-acid sub- 

 stances (leucin, tyrosin, arginin, aspartic acid, etc.), considered the end- 

 products of tryptic proteolysis, it is now suspected by many that the albu- 

 moses and some albumins are synthetic products of the action of an 



