THE NUTRIENTS AND NUTRITION 315 



out the f^'reat vital significance of the pancreas in birds. He 

 removed the organ, and observed that while the subjects 

 endured tlie operation well, starch passed through the gastro- 

 intestinal tract undigested, and death resulted in from ten 

 to twelve days." 



Liver. — At practically the same time that the pancreatic 

 juice enters the intestine the bile from the liver is also poured 

 in. The function of the bile is to aid in the digestion of fat 

 by furnishing the alkali with which it may unite to take on a 

 soluble form. It also aids in neutralizing the acid of the 

 gastric juice received from the gizzard, so that the pancreatic 

 juice may have the proper medium for activity. The liver 

 of tlie chick contains glycogen on the twentieth day of 

 incubation.' 



Besides secreting the bile, an eminently necessarj' contri- 

 bution to digestion, the liver of the goose has been demon- 

 strated by Minkowski (as cjuoted by Brown') to be the seat 

 of much of the synthesis of the uric acid that escapes 

 in the urine. It is also the seat of the manufacture of 

 glycogen, a carbohydrate whose function is to furnish energy 

 to the muscles throughout the body. 



Intestine. — The walls of that portion of the intestine which 

 forms the duodenal loop probably secrete no digestive fluids. 

 Further on it secretes a fluid (succus entericus) which con- 

 tains erepsin and the invertases. Erepsin is an enzyme which 

 carries to a conclusion the work of digesting the protein. 

 The invertases are enzymes which have the power of 

 converting more or less complex sugars into simple ones, 

 capable of absorption. 



It w'ill be noticed that there has been no provision for the 

 digestion of crude fiber. So far as the all too few digestion 

 trials show, crude fiber is almost entirely undigested by 

 chickens and geese. In the first three compartments of the 

 stomach of ruminants and in the cecum of the horse, bacteria 

 have an opportunity to act on crude fiber. 



With fowls, however, bacteria have little opportunity for 

 action. As soon as the hard-coated grains become moist 



' Shaw, American Journal of Physiology, vol. xxxi, No. 7. 

 - Bureau of Animal Industry, Bulletin No. 56. 



