CHAP, i.] DIGESTION. 255 



prepared from an animal some 4 to 10 hours after food has been 

 taken, it is very powerful; prepared from a fasting animal, it is 

 said to exhibit scarcely any action at all. To this point however 

 we shall return immediately. 



Succus Entericus. 



When, in a living animal, a portion of the small intestine is 

 ligatured, so that the secretions coming down from above cannot 

 enter its canal, while yet the blood-supply is maintained as usual, 

 a small amount of secretion collects in its interior. This is spoken 

 of as the succus entericus, and is supposed to be furnished by the 

 glands of Lieberkiihn. We have no exact knowledge how r ever as 

 to the extent to which such a secretion takes place under normal 

 circumstances; and the statements with regard to its action are 

 conflicting. Probably it has no direct action on either fats or 

 proteids; but is amylolytic in some animals, though not in all. 



A small quantity of fluid free from bile, gastric or pancreatic 

 juice, and which may be considered as pure succus entericus, may 

 also be obtained by the following method known as that of Thiry. 

 The small intestine is divided in two places at some distance apart. 

 By fine sutures the lower end of the upper section is united with the 

 upper end of the lower section, thus as it were cutting out a whole piece 

 of the small intestine from the alimentary tract. In successful cases, 

 union between the cut surfaces takes place, and a shortened but other- 

 wise satisfactory canal is re-established. Of the isolated piece the lower 

 end is carefully closed by sutures, while the upper is brought to the 

 wound in the abdominal wall and secured there. A fistula is thus 

 formed, leading into a short piece of intestine quite isolated from the 

 rest of the alimentary canal. 



Succus entericus has also been said to change cane- into grape- 

 sugar, and by a fermentative action to convert cane-sugar into 

 lactic acid, and this again into butyric acid with the evolution of 

 carbonic acid and free hydrogen. 



Of the possible action of other secretions of the alimentary 

 canal, as of the csecum and large intestine, we shall speak when we 

 come to consider the changes in the alimentary canal. 



Concerning the secretion of Brunner's glands our information 

 is at present imperfect. The cells of the glands resemble the 

 central cells of the gastric glands; and an extract of the gland 

 is said to digest fibrin in an acid solution, but to have no distinct 

 amylolytic action. 



