HANDBOOK OF PHYSIOLOGY. 



The Intestinal Secretion, or Succus Entericus. 



On account of the difficulty in isolating the secretion of the glands 

 in the wall of the intestine (Brunner's and Lieberkiihn's) from other 

 secretions poured into the canal (gastric juice, bile, and pancreatic se- 

 cretion), but little is known regarding the composition of the intestinal 

 juice, or succus entericus. 



It is said to be a yellowish alkaline fluid with a specific gravity of 

 1011, and to contain about 2.5 per cent of solid matters (Thiry). 



Functions. The secretion is said to be able to convert proteids into 

 peptones, and to convert starch into sugar, but the evidence in favor of 

 these actions is insufficient. The chief function of the juice is to act 

 upon sugars. It possesses the power of converting cane into grape 

 sugar, and maltose into glucose. It also contains a milk-curdling fer- 

 ment. 



The reaction which represents the conversion of cane sugar into grape 

 sugar may be represented thus : 



2C 12 H 22 O n + 2H 2 = C 12 H 24 12 + C 12 H 24 O 15 

 Saccharose. Water. Dextrose. Laevulose. 



The conversion is probably effected by means of a hydrolytic ferment, 

 invertin (Bernard). 



Summary of the Digestive Changes in 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 an uniform mass all the varieties of food that reach it through the 

 oasophagus, but especially to dissolve the nitrogenous portion by means 

 of its secretion. 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, if not altogether stopped. The soluble matters both those which 

 were so from the first, as sugar and saline matter, and the gastric pep- 

 tones have begun to disappear by absorption into the blood-vessels, and 

 the same thing has befallen such fluids as may have been swallowed. 



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, consists of albuminous matter, broken 

 down, dissolving and half dissolved; fatty matter broken down and 



