322 DIGESTION. 



Intestinal Juice. 



Of the three fluids with, which the food is brought in con- 

 tact in the intestinal canal, namely, the bile, the pancreatic 

 juice, and the intestinal juice, the last, the secretion of 

 the mucous membrane of the intestine, presents the greatest 

 difficulties in the investigation of its properties and function. 

 If it be admissible to reason from the known mechanism 

 of secretion in other parts, it is fair to suppose that the 

 normal secretion from the mucous membrane of the intestine 

 can only take place in obedience to the stimulus of food. 

 The same cause induces the secretion of the pancreatic juice, 

 and increases the flow of bile. As we have already seen, the 

 food, as it passes from the stomach into the duodenum, is to 

 a great extent disintegrated and mingled with the secretions 

 from both the mouth and the stomach. Under these circum- 

 stances, it is evidently impossible, in the present state of the 

 science, to collect the intestinal juice under perfectly phys- 

 iological conditions, in a state of purity sufficient to allow of 

 extended experiments regarding its composition, properties, 

 and action in digestion. It is for these reasons that we 

 cannot regard the observations of Frerichs and Bidder and 

 Schmidt as, of themselves, throwing much light upon the 

 properties and function of the fluid under consideration. 



Frerichs attempted to collect the intestinal juice in the 

 following way : He drew out from the abdomen of a living 

 animal a loop of the small intestine, from four to eight 

 inches in length, which was emptied, carefully cleaned by 

 repeated washings with warm water, and isolated by two 

 ligatures. The intestine was then returned to the abdomi- 

 nal cavity, the animal was killed after a few hours, and the 

 contents of the isolated portion examined. These experi- 

 ments were made upon dogs and cats, during the intervals of 

 digestion. The fluid contained in the portion of intestine 

 situated between the ligatures was found to be transparent, 

 colorless, and viscid, with a strongly alkaline reaction. It 



