INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 151 



intestinal fluids are the active agents in its digestion during life. 

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

 a short time after the meal, the stomach is found to contain starch 

 but no sugar ; while in the small intestine there is an abundance of 

 sugar, and but little or no starch. If some observers have failed 

 to detect sugar in the intestine after feeding the animal with 

 starch, it is because they have delayed the examination until too 

 late. For it is remarkable how rapidly starchy substances, if pre- 

 viously disintegrated by boiling, are disposed of in the digestive 

 process. If a dog, for example, be fed as above with boiled starch 

 and meat, while some of the meat remains in the stomach for 

 eight, nine, or ten hours, the starch begins immediately to pass into 

 the intestine, where it is at once converted into sugar, and then as 

 rapidly absorbed. The whole of the starch may be converted into 

 sugar, and completely absorbed, in an hour's time. We have even 

 found, at the end of three-quarters of an hour, after a tolerably 

 full meal of boiled starch and meat, that all trace of both starch 

 and sugar had disappeared from both stomach and intestine. The 

 rapidity with which this passage of the starch into the duodenum 

 takes place varies, to some 



extent, in different animals, Flg< 31 * 



according to the general ac- 

 tivity of the digestive appa- 

 ratus ; but it is always a 

 comparatively rapid process, 

 when the starch is already 

 liquefied and is administered 

 in a pure form. There can 

 be no doubt that the natural 

 place for the digestion of 

 starchy matters is the small 

 intestine, and that it is ac- 

 complished by the action of 

 the intestinal juices. 



Our knowledge is not very 

 complete with regard to the 

 exact nature of the fluids by which this digestion of the starch is 

 accomplished. The juices taken from the duodenum are generally 

 a mixture of three different secretions, viz., the bile, the pancreatic 

 fluid, and the intestinal juice proper. Of these, the bile may be 

 left out of the question ; since it does not, when in a pure state, 



FOLLICLES OF LIEBKRKCHN, f.om Small 

 testine of dog. 



la- 



