DIGESTION IN SMALL INTESTINE. 343 



whole period of gastric digestion, is being constantly 

 squeezed or strained through the pyloric orifice into the 

 duodenum, consists of albuminous matter, broken down, 

 dissolving and half dissolved, fatty matter, broken down, 

 but not dissolved at all, starch very slowly becoming sugar, 

 and as it becomes sugar, also dissolving in the fluids with 

 which it is mixed, while with these are mingled gastric 

 fluid, and fluid that has been swallowed, together with 

 such portions of the food as are not digestible, and will be 

 finally expelled as part of the faeces. 



On the entrance of the chyme into the duodenum, it is 

 subjected to the influence of the fluid secreted by Lieber- 

 kiihn's and Brunn's glands, before described, and to that 

 of the bile and pancreatic juice, which are poured into this 

 part of the intestine. 



Without doubt, that part of digestion which it is the 

 chief duty of the small intestine to perform, is the altera- 

 tion of the fat in such a manner as to make it fit for 

 absorption. And there is no doubt that this change is 

 chiefly effected in the upper part of the small intestine. 

 What is the exact share of the process, however, allotted 

 respectively to the bile, pancreatic secretion, and the secre- 

 tion of the intestinal glands, is still uncertain. It is most 

 probable, however, that the pancreatic secretion, and the 

 bile are the main agents in emulsifying the fat, and that 

 they do this by direct admixture with it. They also pro- 

 mote its absorption by moistening the surface of the villi 

 (P- 3 36). 



During digestion in the small intestine, the villi become 

 turgid with blood, their epithelial cells become filled, by 

 absorption, with fat globules, which, after minute division, 

 transude into the granular basis of the villus, and thence 

 into the lacteal vessel in the centre, by which they are 

 conveyed along the mesentery to the lymphatic glands, 

 and thence into the thoracic duct. The term chyle is 

 sometimes applied to the emulsified contents of the intes- 



