132 DIGESTION 



side of the liver. This fluid is of a greenish-yellow color, 

 having a peculiar smell, and a very bitter taste. (Head Note 7.) 



34. The pancreatic juice is the product of a gland called the 

 pancreas, situated behind the stomach. This fluid is colorless, 

 watery, Alkaline, and without odor. Like the digestive -juices 

 previously described, it owes its solvent power to its peculiar 

 ferments. The most important of these ferments, called pan- 

 creatin, transforms starch into sugar. Another, tryp&n, causes 

 the solution of undissolved albuminoid substances ; and a thircT 

 ferment, which has not received a name, causes a partial acidi- 

 fication of the fats. By the joint action of these fluids, the 

 food is prepared for absorption. There results from this action 

 of the pancreatic juice a white and milky fluid,- termed the 

 chyle, which holds in solution the digestible portions of the 

 food, and is spread over the extensive absorbent surface of 

 the small intestines. (Head Note 8.) 



35. The mucous membrane of the intestines, also, secretes 

 or produces a digestive fluid by means of numerous " follicles," 

 or minute glands ; this is called the intestinal juice. Erom 

 experiments on the lower animals, it has been ascertained that 

 this fluid exerts a solvent influence over each of the three 

 organic food principles, and in this way completes the action 

 of the fluids previously mentioned, viz.: of the saliva in 

 converting starch into sugar, of the gastric juice in digesting 

 the albuminoids, and of the pancreatic juice and bile in 

 emulsifying the fats. 



7. Experiment. Bile. The chief function of the bile in the diges- 

 tion of food is the emulsifying of fats. 



If a quantity of oil is shaken up with an equal part of water in a test- 

 tube, the two will not mix. But if we substitute bile for the water, and 

 shake thoroughly, we obtain an emulsion which will separate but slowly 

 and imperfectly. 



The bile may be obtained from the gall-bladder of the ox or sheep at 

 any butcher's or slaughter-house. 



8. Experiment. Pancreatic Juice. To obtain the pancreatic juice, 

 it will be necessary to extract it from a fresh pancreas, "sweet-bread" 



84. The pancreatic juice ? The joint action of these fluids ? 



85. The mucous membrane ? Experiments on inferior animals ? 



