THE BILE 809 



or section of the splanchnic nerves causes a condition of diarrhoea 

 which may last for two or three days. This condition might be 

 determined either by an increased motor activity of the gut, or by 

 removal of inhibitory impulses normally arriving at the intestinal 

 glands. Such a view receives support from an experiment first 

 performed by Moreau. The abdomen of a dog is opened under an 

 anaesthetic, and three contiguous loops of small intestine are separated 

 by means of ligatures from the rest of the gut. The middle loop 

 is then denervated by destruction of all the nerve fibres lying, on 

 its blood-vessels, as they course through the mesentery, care being 

 taken not to injure the blood-vessels themselves. The loops are 

 then replaced in the abdomen and the animal left from four to sixteen 

 hours. On killing the animal at the end of this time, it is often 

 found that the middle loop, i.e. the denervated loop, is distended 

 with fluid having all the properties of ordinary intestinal juice, whereas 

 the other two loops are empty. A series of comparative experi- 

 ments by Mendel and by Falloise have shown that the secretion 

 begins about four hours after the operation, increases for about 

 twelve hours, and then rapidly declines, so that at the end of two 

 days all three loops will be found empty. This has often been inter- 

 preted as due to the removal of inhibitory impulses passing from 

 the central nervous system to the local secretory mechanism, and 

 we have no direct evidence which can be adduced against such a 

 view. It is possible, however, that the hypersemia of the gut, which 

 is produced by the processes of denervation, may be sufficient to 

 account for the increased formation of intestinal juice, since the 

 hypersemia will tend to pass off as the vessels recover a local tone. 



It is not possible to explain the flow of intestinal juice which 

 follows a meal by any assumption of nervous impulses transmitted 

 through the local nerve plexuses of the gut, since these have been 

 divided in the making of the fistula. If we exclude a nervous reflex 

 action by the long paths, namely, through the spinal cord and the 

 sympathetic or vagus nerves, the flow which attends the passage of 

 food into the first part of the duodenum must be excited by the 

 formation of some chemical messenger. As to the existence of such 

 a chemical messenger or hormone for the intestinal secretion there 

 can be no doubt, but the evidence as to its precise nature is at present 

 conflicting. It is stated by Pawlow that the most effective stimulus 

 to the flow of succus entericus is the presence of pancreatic juice 

 in the loop of gut. No evidence has yet been brought forward that 

 injection of pancreatic juice into the blood stream will cause any 

 flow of intestinal juice. On the other hand, Delezenne and Frouiii 

 have shown that in animals provided with a permanent fistula 

 involving the duodenum or upper part of the jejunum, intravenous 



