112 HUMAN PHYSIOLOGY. 



combined with the intestinal movements. The neutral fats are also 

 decomposed into their corresponding fatty acids and glycerin; 

 The acids thus set free unite with the alkaline bases present, in the 

 intestine and form soaps. This decomposition of the neutral fats 

 is caused by the ferment, steapsin. 



The bile has an important function in the elaboration of the food 

 and in its preparation for absorption. It is a golden-brown, viscid 

 fluid, having a neutral or alkaline reaction and a specific gravity 

 of 1020. 



COMPOSITION OF BILE. 



Water 859.2 



Sodium glycocholate -\ 

 Sodium taurocholate [ 



Fat 9.2 



Cholesterin 2.6 



Mucus and coloring-matter 29.8 



Salts 7-8 



1,000.0 



The biliary salts, sodium glycocholate and taurocholate, are char- 

 acteristic ingredients, and by the process of secretion are formed in 

 the liver from materials furnished by the blood. It. is probable 

 that they are derived from the nitrogenized compounds, though the 

 stages in the process are unknown. They are reabsorbed from the 

 small intestine to play some ulterior part in nutrition. 



Cholesterin is a product of waste taken up by the blood from the 

 nerve tissues and excreted by the liver. It crystallizes in the form 

 of rhombic plates which are quite transparent. When retained 

 within the blood, it gives rise to the condition of cholesteremia, 

 attended with severe nervous symptoms.'' It is given off in the 

 feces under the form of stercorin. 



The coloring-matters which give the tints to the bile are biliverdin 

 and bilirubin, and are probably derived from the coloring-matter of 

 the blood. Their presence in any fluid can be recognized by adding 

 to it nitric acid containing nitrous acid, when a play of colors is 

 observed, beginning with green, blue, violet, red and yellow. 



The bile is both a secretion and an excretion ; it is constantly 

 being formed and discharged by the hepatic ducts into the gall- 



