CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 363 



of giving rise, by digestion, to peptone ; but it may be doubted, as 

 in the case of pepsin and other ferments, whether the pure ferment 

 has yet been isolated. There are no means of distinguishing the 

 amylolytic ferment of the pancreas from ptyalin. The term pan- 

 creatin has been variously applied to many different preparations 

 from the gland, and its use had perhaps better be avoided. 



The action of pancreatic juice, or of the infusion or extract of 

 the gland, on starch, is seen under all circumstances, whether the 

 animal be fasting or not. The same may probably be said of the 

 action on fats. On proteids the natural juice, when secreted in a 

 normal state, is always active. The glycerine extract or aqueous 

 infusion of the gland, on the contrary, as we have already explained, 

 200, is active in proportion as the trypsinogen has been converted 

 into trypsin. 



Succus Entericus. 



211. 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, of which we shall 

 presently speak. 



Succus entericus may be obtained by the following method, known 

 as that of Thiry modified by Vella. The small intestine is divided in 

 two places at some distance (30 to 50 cm.) apart. By fine sutures the 

 lower end of the upper section is carefully 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 otherwise 

 satisfactory canal is re-established. Of the isolated piece the two 

 ends are separately brought through incisions in the abdominal wall 

 and their mouths carefully fastened in such a manner that each mouth 

 of the piece opens on to the exterior. During the process of healing 

 two fistulae are thus established, one leading to the beginning of and 

 the other to the end of a short piece of intestine quite isolated from 

 the rest of the alimentary canal ; by means of these openings a small 

 quantity of fluid can be obtained. 



The quantity secreted is said to be considerably increased by the 

 administration of pilocarpin. 



Succus entericus obtained from the dog by the above method 

 is a clear yellowish fluid having a faintly alkaline reaction and 

 containing a certain quantity of mucus. It is said to convert 

 starch into sugar, and proteids into peptone (the action being very 

 similar to that of pancreatic juice), to split up neutral fats, to 

 emulsify fats and to curdle milk. It is also said to invert cane- 

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



