DIGESTION. 173 



gradual and leaves for some time a part of the starch unchanged. 

 Kroeger found that one gramme of fresh pancreatic juice, at the tem- 

 perature of 35 C., transformed into glucose, within thirty minutes, 

 4.67 grammes of starch ; while, according to our own observations, 

 one gramme of fresh human saliva, mixed at 38 C. with a watery 

 solution containing less than 0.1 gramme of boiled starch, though it 

 gives a manifest sugar reaction in one minute, still contains a large 

 portion of unaltered starch at the end of an hour. According to 

 various observers (Bouchardat and Sandras, Ranke, Gorup-Besanez), 

 pancreatic juice also causes the transformation of raw starch, a prop- 

 erty which was found b\* Bouchardat to be very energetic in the 

 secretion of the common fowl. 



Starch which has passed the stomach unchanged is thus promptly 

 transformed into glucose after entering the duodenum. In dogs, fed 

 with a mixture of meat and boiled starch, and killed at various periods 

 after feeding, starch is for a time abundantly recognizable in the stomach 

 without traces of glucose, while in the fluids of the small intestine it 

 is absent and glucose takes its place. According to Langendorff,* 

 exclusion of the pancreatic juice from the intestine in pigeons arrests 

 so completely the digestion and assimilation of starch, that these 

 animals die after considerable emaciation, in from six to twelve days. 

 This secretion is plainly the principal agent in the digestion of starch, 

 and as starchy substances constitute, in man, rather more than one-half 

 the entire food, its function is hardly second in importance to any other 

 in the alimentary canal. 



It is le-s easy to judge of the pancreatic juice, as an agent in the 

 solution of albuminous matters. Some writers attribute much impor- 

 tance to this action, owing to its striking character in artificial diges- 

 tions. But it is hardly safe to assume that these experiments represent 

 fully the phenomena of intestinal digestion. In the alimentary canal 

 a number of different secretions are in operation together or succes- 

 sively, and the properties of each may be more or less modified by the 

 time of its secretion, or the proportion in which it is mingled with the 

 others. The action of pancreatic juice on albumenoids is most marked 

 in an alkaline menstruum, and is diminished or arrested by an acidity 

 less than that of the gastric juice. But the reaction of the small 

 intestine in carnivorous animals, during digestion, is acid. According 

 to Bernardf this is always the case. In our own experiments, with a 

 duodenal fistula in the dog, the fluids of the intestine became acid as 

 soon as the contents of the stomach began to pass the pylorus. Accord- 

 ing to Schmidt-Mulheim.J who operated by killing the animals at 

 various periods after feeding and examining the intestinal contents, 

 the reaction of the dog's small intestine during the digestion of meat 



*Archiv fur Anatomie und Physiologic. Leipzig, 1879, p. 26. 



f Liquides de FOrganisme. Paris, 1859, tome ii., p. 347. 



j Archiv fiir Anatomic und Physiologie. Leipzig, 1879, p. 39. 



