270 DIGESTION. 



nection with the influence of the nervous system on the pro- 

 duction of glucose. 



Summary of the Changes which take place in the Food during its 

 Passage through the Small Intestine. 



In order to understand the changes in the food which occur 

 during its passage through the small intestine, it will be well 

 to refer briefly to the state in which it leaves the stomach 

 through the pylorus. It has been said before, that the chief 

 office of the stomach is not only to mix into a uniform mass 

 all the varieties of food that reach it through the oesophagus, 

 but especially to dissolve the nitrogenous portion by means of 

 the gastric juice. The fatty matters, during their sojourn in 

 the stomach, become more thoroughly mingled with the other 

 constituents of the food taken, but are not yet in a state fit for 

 absorption. The conversion of starch into sugar, which began 

 in the mouth, has been interfered with, although not stopped 

 altogether. The soluble matters both those which were so 

 from the first, as sugar and saline matter, and those which 

 have been made so by the action of the saliva and gastric 

 juice have begun to disappear by absorption into the blood- 

 vessels, and the same thing has befallen such fluids as may 

 have been swallowed, wine, water, &c. 



The thin pultaceous chyme, therefore, which during the 

 whole period of gastric digestion, is being constantly squeezed 

 or strained through the pyloric orifice into the duodenum, con- 

 sists of albuminous matter, broken down, dissolving and half 

 dissolved, fatty matter, broken down, but not dissolved at all, 

 starch very slowly in process of conversion into 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 fseces. 



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

 jected to the influence of the fluid secreted by Lieberkiihn'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 a chief 

 duty of the small intestine to perform, is the alteration 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 



