130 PHYSIOLOGY CHAP. 



U. Lontbroso opposes this theory by a number of data worked 

 out in our laboratory. He observed the secretion in a Vella's 

 loop, made at a certain distance from the duodenum, on many 

 occasions, and for many hours. He has proved that there is 

 always a very scanty secretion (4-6 c.c. of juice) in 6 to 8 hours, even 

 after meals that are rich in flesh and fat, or consist of fat alone. 

 But if a solution of oleic acid or of soap is introduced directly into 

 the loop, an abundant secretion is at once called out. With 25 c.c. 

 oleic acid dissolved in bile, it is possible in a few minutes to obtain 

 30-40 c.c. or more of succus entericus. 



It is a familiar fact that soap and fatty acid dissolved in bile 

 are found throughout the intestine after giving fats. If no 

 secretion occurs in Vella's loop, even after the digestion of large 

 quantities of fats, this must mean that the hormones which 

 activate secretion in the isolated tract of the loop are either not 

 produced or not absorbed during digestion. 



But if it be proved that enteric secretion is not excited by 

 hormone stimuli ; if, on the other hand, Lombroso's observations 

 tell against the hypothesis that the mesenteric nerves convey the 

 secretory stimuli to the intestinal mucosa (as we said above, they 

 appear rather to have the task of inhibiting the intestinal secretion), 

 the question still remains open as to whether the said secretion 

 results solely from the direct action of chemical stimuli, or if these 

 may determine it by reflex paths from other regions that are not 

 directly excited, e.g. the stomach. 



Lombroso's observations on the ordinary Vella's loop have not 

 solved the problem, because the operative act completely destroys 

 the relations of continuity of the nerves that run throughout the 

 extent of the intestinal walls, so that they can no longer propagate 

 the secretory stimuli. 



Lombroso has accordingly modified his method of operation. 

 He separates a fairly long segment of intestine (50-80 cm.) as if 

 making a Vella's loop. After suturing the two extreme ends of 

 the divided portion to the abdominal walls, he attaches 3-4 cm. of 

 the middle part of the loop to the same wall. When adhesion 

 takes place, i.e. in 3 to 4 days, he slits up the middle of the loop so 

 as to bring it into relation with the exterior. This produces twin 

 loops of Vella, which preserve connection with the nerve plexuses 

 that run along the coats of the intestine. 



On introducing a substance that excites secretion into the 

 first loop, the second loop does not secrete unless the same sub- 

 stance is made to pass into it by bringing the two lips together. 

 This indicates that direct action of the proper chemical stimuli 

 on the mucous membrane is necessary to excite the intestinal 

 secretion. 



XVIII. The Liver in -its structure and functions is a gland, 

 which in adult man weighs about 1579 grins. (1526 grms. in 



