PHENOMENA OF INTESTINAL DIGESTION. 157 



bv the influence of which its chemical transformation and solution 

 are commenced. If the meal consist wholly or partially of mus- 

 cular flesh, the first effect of the gastric juice is to dissolve the 

 intervening cellular substance, by which the tissue is disintegrated 

 and the muscular fibres separated from each other. Afterward 

 the muscular fibres themselves become swollen and softened by 

 the imbibition of the gastric fluid, and are finally disintegrated 

 and liquefied. In the small intestine, the pancreatic and intestinal 

 juices convert the starchy ingredients of the food into sugar, and 

 break up the fatty matters into a fine emulsion, by which they are 

 converted into chyle. 



Although the separate actions of these digestive fluids, however, 

 commence at different points of the alimentary canal, they after- 

 ward go on simultaneously in the small intestine ; and the changes 

 which take place here, and which constitute the process of intestinal 

 digestion, form at the same time one of the most complicated, and 

 one of the most important parts of the whole digestive function. 



The phenomena of intestinal digestion may be studied, in the 

 dog, by killing the animal at various periods after feeding, and 

 examining the contents of the intestine. We have also succeeded, 

 by establishing in the same animal an artificial intestinal fistula, 

 in gaining still more satisfactory information on this point. The 

 fistula may be established, for this purpose, by an operation precisely 

 similar to that already described as employed for the production of 

 a permanent fistula in the stomach. The silver tube having been 

 introduced into the lower part of the duodenum, the wound is 

 allowed to heal, and the intestinal secretions may then be with- 

 drawn at will, and subjected to examination at different periods 

 during digestion. 



By examining in this way, from time to time, the intestinal 

 fluids, it at once becomes manifest that the action of the gastric 

 juice, in the digestion of albuminoid substances, is not confined to 

 the stomach, but continues after the food has passed into the intes- 

 tine. About half an hour after the ingestion of a meal, the gastric 

 juice begins to pass into the duodenum, where it may be recognized 

 by its strongly-marked acidity, and by its peculiar action, already 

 described, in interfering with Trommer's test for grape sugar. It 

 has accordingly already dissolved some of the ingredients of the 

 food while still in the stomach, and contains a certain quantity of 

 albuminose in solution. It soon afterward, as it continues to pass 

 into the duodenum, becomes mingled with the debris of muscular 



