344 MANUAL OF ZOOLOGY SECT. 



there are numerous small glands, the buccal glands, in the 

 wall of the buccal cavity. The secretion of the salivary 

 glands, the saliva, enters the cavity of the mouth through 

 the ducts of the glands; it contains a ferment, ptyalin, 

 which has the property of converting starch into sugar. 

 The liver is in all three a relatively large organ, fixed by 

 folds of peritoneum to the dorsal wall of the abdominal 

 cavity, and divided by fissures into a number of lobes. Its 

 duct, the bile-duct ', conveys its secretion, the bile, into 

 the most anterior part of the intestine, known as the 

 duodenum. The duct gives off a diverticulum which 

 expands into a rounded sac, the gall-bladder; this acts 

 as a receptacle for the bile when it is not required. The 

 bile has an important action on the fatty matters of the food, 

 converting them into an emulsion, and decomposing a small 

 proportion into glycerine and fatty acid. In addition to 

 secreting the bile the liver has another function to perform ; 

 it acts as a storehouse for surplus carbohydrates ab- 

 sorbed from the food. The carbohydrates compounds 

 of the nature of starch and sugar are converted 

 in the liver into a substance known as glycogen or animal 

 starch, which b'ecomes stored up in the cells to be given out 

 again to the blood as it is required for nutrition during the 

 intervals of fasting : this function of the liver is known as 

 the glycogenic function. 



The pancreas, which is a much smaller gland than the 

 liver, produces a secretion, the pancreatic juice, which has 

 the effect of converting starch into sugar, proteids into 

 soluble modifications known as peptones, and of assisting in 

 the emulsification of fats. The duct of the pancreas 

 also opens into the duodenum. The nutrient matters of 

 the food, rendered soluble by the action of the various 

 digestive fluids, pass into the blood contained in the blood- 



