184 DIGESTION. 



by direct observation, is a comparatively scanty, alkaline fluid, contain- 

 ing an albuminous ingredient capable of coagulation by heat. It exerts 

 an action upon starchy and fatty matters similar to that of the pancreatic 

 juice, but less energetic in operation. Its action upon albuminous 

 matters is less distinct, and has sometimes been found to be absent or 

 feebly developed. It is undoubtedly of importance as accessory to the 

 other digestive secretions, but the precise mode and extent of its opera- 

 tion have not yet been determined. 



In the process of intestinal digestion a number of different actions 

 are going on at the same time. The materials of the food, disinte- 

 grated and partly dissolved in the stomach, pass through the pylorus 

 into the intestine still mingled with a notable quantity of gastric juice, 

 and are there subjected to the action of the remaining digestive secre- 

 tions. Hydrated starch, set free by the solution of the albuminous 

 matters with which it was associated, rapidly undergoes the conver- 

 sion into glucose, and the saccharine fluid so produced is promptly ab- 

 sorbed. If a dog be fed with a mixture of meat and boiled starch, 

 although this conversion does not begin until the fluids enter the duo- 

 denum, we have found, in some instances, that at the end of three- 

 quarters of an hour all traces of both starch and sugar had disappeared 

 from both stomach and intestine. Raw starch in the lower animals is 

 digested more slowly but in a similar manner. Bouchardat and Sandras, 

 in examining the alimentary canal of the rabbit when fed with potato, 

 found the grains of starch only slightly changed in the stomach, but in 

 the small intestine they were altered, corroded, and more or less dis- 

 solved in proportion as they had descended the intestinal canal, while in 

 the rectum only feeble traces of them remained. 



All observers agree that cane sugar undergoes the transformation 

 into glucose by contact with the intestinal juices. This conversion 

 may be slowly effected by the action of gastric juice alone. If one 

 part of cane sugar be dissolved in 20 parts of dog's gastric juice, and 

 kept at 38 (lOtPF.) the mixture will give traces of glucose at the end 

 of two hours, and in three hours its quantity is considerable. It cannot 

 be shown, however, that the gastric juice exerts this effect on sugar dur- 

 ing ordinary digestion. If pure cane sugar be given to a dog with a 

 gastric fistula while digestion of meat is going on, it disappears in from 

 two to three hours, without any glucose being detected in the fluids 

 withdrawn from the stomach. It is, therefore, either directly absorbed 

 under the form of cane sugar, or passes, little by little, into the duode- 

 num, where the intestinal fluids convert it into glucose. 



Fatty matters, which are simply melted in the stomach, or set free by 

 the liquefaction of the tissues which contain them, on entering the intes- 

 tine begin to be emulsified by the pancreatic and intestinal juices. This 

 process continues throughout the small intestine, together with the com- 

 plete solution of muscular flesh which has been disintegrated by stomach 

 digestion. If a dog, with a permanent duodenal fistula, be examined 

 during the digestion of animal food, the fluid drawn from the fistula 



