220 INTESTINAL DIGESTION 



Action of the Pancreatic Juice on Carbohydrates. The action of the 

 pancreatic juice in transforming starch into sugar was first observed 

 in 1844, by Valentin, who experimented with an artificial liquid made 

 by infusing pieces of the pancreas in water. Bouchardat and Sandras 

 first noted this property in the normal pancreatic secretion. In man, 

 some of the amylaceous matters are acted on by the saliva, but most 

 of the starch taken as food is rapidly digested in the small intestine. 

 It is possible that the bile assists in this process to a slight extent. 

 In the transformation of starch into sugar in the small intestine, the 

 same intermediate processes are observed as occur in the action of the 

 saliva ; but the change in the intestine into glucose is more rapid. 

 It is stated that amylopsin is not present in the pancreas of the new- 

 born infant (Korowin), and that in early infancy before the second or 

 third month the pancreatic extract will not digest starch. 



As cane-sugar passes from the stomach into the duodenum, it is 

 almost instantly inverted ; but this is due entirely to the action of the 

 intestinal juice. The pancreatic juice does not act on the sugars. 



Action of the Pancreatic Juice on Proteids. Reference has already 

 been made to the relative importance of intestinal digestion ; and it has 

 been apparent that the process of disintegration of food in the stomach 

 is not final, even as regards many of the nitrogenous substances, but 

 is rather preparatory to the complete liquefaction of these matters, 

 which takes place in the small intestine. In experiments in which the 

 pancreas has been partially destroyed in dogs, there was rapid emacia- 

 tion, with great voracity, and the passage, not only of unchanged fats 

 and starch, but of undigested nitrogenous matters in the dejections. 

 The voracious appetite, progressive emaciation and the passage of all 

 classes of alimentary substances in the f eces, after this operation, in- 

 dicate the great importance of the pancreatic juice in digestion ; but 

 the precise mode of action on the proteids is even now a question of 

 some obscurity. If the bile is shut off from the intestine and dis- 

 charged externally by a fistulous opening, the same voracity and ema- 

 ciation are observed ; and yet there is no single alimentary substance 

 on which the bile, of itself, has been shown to exert a decided digestive 

 action. Furthermore, the pancreatic juice evidently is adapted to act 

 on alimentary % matters after they have been subjected to the action of 

 the stomach, a preparation that is essential to proper intestinal diges- 

 tion ; and once passed into the intestine, the food comes in contact with 

 a mixture of pancreatic juice, intestinal juice and bile. Nitrogenous 

 alimentary substances, when exposed to the action of the pancreatic 

 juice out of the body, rapidly become softened and dissolved in some 

 of their parts, but soon undergo putrefaction. Analogous changes take 



