194 ANATOMY FOR NURSES. [Chap. XVI. 



envelopes of the fat-cell and set the fat free, but it has no 

 power to emulsify them. The essential property of gastric 

 juice is the power it has of decomposing proteid matters and 

 of converting them into a soluble substance called peptone. 

 Whatever the proteid may be, whether the albumin of eggs, 

 the gluten of flour in bread, the myosin in flesh, the result is 

 the same, pepsin, in conjunction with an acid at the temperature 

 of the body, transforms them into peptones. 



Peptones readily dissolve in water, and pass with ease through 

 animal membranes. They are probably absorbed, as soon as 

 formed, by the blood-vessels in the walls of the stomach, though 

 some pass in the chyme through the pylorus into the small 

 intestine. 



Changes the food undergoes in the small intestine. — The chyme 

 on entering the duodenum, after an ordinary meal, is a mixture 

 of various matters. It contains some undigested proteids ; some 

 undigested starch ; oils from fats eaten ; peptones formed in the 

 stomach, but not yet absorbed ; salines and sugar which have 

 also escaped complete absorption in the stomach ; all mixed with 

 a good deal of water and the secretions of the alimentary canal. 

 This acid mixture passing into the duodenum excites reflexly 

 the secretory action of the pancreas, and stimulates the bile to 

 flow from the gall-bladder ; the glands of Lieberkiihn also be- 

 come active, and all these secretions proceed to further change 

 the food-stuffs that have escaped digestion in the stomach. 



Bile. — Bile, secreted in the lobules of the liver and stored in 

 the gall-bladder until needed, is a fluid of a bright golden red 

 colour, with an alkaline reaction. The chief solid constituents 

 of bile are cholesterin, the bile-salts, and the colouring-matters 

 or pigments. 



Action of bile on food. — Upon proteids and starch, bile has 

 little or no digestive action. On fats, it has a slight solvent 

 action, and, in conjunction with pancreatic juice, has the power 

 to emulsify them. When bile is prevented from flowing into the 

 alimentary canal, the contents of the intestine undergo changes 

 which do not otherwise take place, and which lead to the devel- 

 opment of various products, especially of ill-smelling gases. 

 Lastly, the passage of fats through membranes is assisted by 

 wetting the membranes with bile or with a solution of bile- 

 salts. It is known that oil will pass to a certain extent through 



