440 INTERNAL SECRETION 



according to Pawlow, first, by the mechanical stretching of the 

 intestinal canal, and second, by the presence of the pancreatic 

 juice. Bayliss and Starling believe it probable that the flow of 

 intestinal juice from the glands in the intestinal wall is provoked 

 by the chemical stimulus supplied by the pancreatic secretion ; 

 while Delezenne and Frouin hold the view that the discharge of 

 all the three secretions which are active in the upper part of the 

 small intestine, namely, the bile, the pancreatic fluid, and the 

 intestinal fluid, is effected by the same mechanism, namely, the 

 elaboration of secretin in the intestinal mucosa after the passage 

 into the intestine of the acid contents of the stomach. 



According to Frouin, the elaboration of secretion by the 

 intestine may be increased by the intravenous injection of intes- 

 tinal fluid. 



Pawlow's careful experiments have shown that the secretion 

 of the gastric fluid is largely the outcome of nervous impulses. 

 But two to three hours after food the gastric secretion becomes 

 increased ; according to Pawlow, this increase is maintained after 

 resection of the vagi, and it appears to be dependent upon the 

 nature of the food. 



Edkins next discovered that an extract is obtainable from 

 the pyloric mucous membrane by extraction with hydrochloric 

 acid, as well as by rubbing down with dextrose, maltose, or 

 peptone. When injected into the veins in repeated small doses, 

 this extract causes secretion of the gastric juice. According to 

 Edkins, the active substance, gastrin, is not destroyed by boiling 

 and appears to belong to the same class of bodies as pancreatic 

 secretin. This " gastric secretin," as Starling calls it, is present 

 only in the pyloric mucosa, extracts of the mucous membrane of 

 the fundus being inactive. 



THE INTERNAL SECRETION OF THE KIDNEY. 



The assumption of an internal secretory function on the part 

 of the kidney is among the earliest dicta of the Brown-Sequard 

 doctrine. As early as 1869, Brown-Sequard suggested that 

 uraemia either was not, or was not exclusively, the result of the 

 accumulation of urinary constituents in the blood, but was due to 

 suppression of the internal secretion of the kidney. Following 

 his first experiments with testicular extract, Brown-Sequard with 

 d'Arsonval endeavoured to obtain practical proof of his assump- 

 tion. A large number of clinical observations of anuria of long 

 duration, in which uraemic symptoms were almost entirely absent, 

 led him to conclude that the occurrence of uraemia does not depend 

 solely upon the presence of urinary constituents in the blood, and 

 that it is not the result of stimuli supplied by the diseased 

 kidney; but that it is principally due to changes in the chemical 

 composition of the blood, brought about by suppression of the 



