THE FEED PROBLEM 261 



(4) To guard against the introduction of noxious gases and 

 other poisons, as ammonia, and to transform them into urea. 



(5) To neutrahze poisons. 



(6) To excrete cholesterin. 



(7) To furnish alkah bases. 



(8) To facilitate absorption of digested fats. 



(9) To guard against infection from the intestines. 

 Intestinal Digestive Juices. — ^In addition to the pancreatic 



juice and bile, the food, when emptied from the gizzard into 

 the intestines, meets a third fluid, the succus entericus, which 

 fluid is secreted by glands located in the wall of the small 

 intestines. This digestive fluid contains several ferments, as 

 follows : 



(1) Erepsin, acting upon protein, converting peptone and 

 deutro-albumoses into hexone bases and amino-acids. 



(2) Maltase, acting upon sugars, converting dextrin and 

 maltose into dextrose. 



(3) Lactase, acting on sugar, converting milk-sugar into 

 dextrose and galactose. 



(4) Invertase, acting on sugar, converting cane-sugar into 

 dextrose and levulose. 



(5) Enterokinase, which possesses the power of activating the 

 trypsinogen of the pancreatic juice, converting it into trypsin. 



(6) A substance called secretin, which is secreted and ab- 

 sorbed and causes a stimulation of the pancreatic secretion. 



Absorption of Digested Nutrients. — The lymph system is 

 the drainage or sewage system of the body. 



Lymph is a liquid by which the tissues of the body are nour- 

 ished and which collects the waste or effete material from the 

 tissues and carries it to the blood, through which channels it 

 i-s carried to the various excretory organs and eliminated from 

 the body. 



Ljntnph circulates in vessels called lymphatic vessels, and 

 this vascular system is called the lymphatic system. 



The tissues are bathed in lymph. Lymph-spaces exist be- 

 tween the lymph capillaries and capillary blood-vessels, and 

 there is a constant passage of fluid laden with nutrients from 

 the blood capillaries into these spaces from which the cells are 

 bathed and nourished. The liquid in these spaces receives the 



