AND ABSORPTION 43 



stimulates also the activity of the liver cells, thus 

 pouring into the bowel not only pancreatic juice 

 but also bile.* 



We find in this mechanism a clear indication for 

 the administration of hydrochloric acid in cases 

 where that of the gastric juice is deficient. At least 

 we may be able to preserve for the patient the 

 activity of his pancreatic juice, which is likely to be 

 suppressed when the usual stimulus is lacking. The 

 exhibition of secretin itself has so far been a failure ; 

 it is not absorbed from the bowel, and giving it 

 subcutaneously produces dangerous depression, due 

 apparently to other substances, which we do not 

 know how to separate, extracted along with it from 

 the duodenal mucous membrane. 



Pawlow and his followers have described a mar- 

 vellous adaptation of the various pancreatic ferments 

 to the work in hand ; thus, they thought that a 

 meat diet called forth much trypsin, and a starchy 

 diet much amylopsin. These statements were made 

 before we knew that the flow of pancreatic juice 

 was started by secretin, which in its turn depends 



* This is only one of several recently discovered chemical 

 messengers, travelling from one part to another in the blood- 

 stream (so-called " hormones," Starling). We have often wondered 

 why the uterus enlarges in extra-uterine gestation ; it is because 

 the internal secretion of the corpus luteum, left by the scar in the 

 ovary of the ruptured Graafian follicles, is the normal stimulus 

 causing the great development of the uterus which takes place 

 during pregnancy. Injection of extract of corpus luteum into a 

 virgin animal of the same species causes such enlargement of the 

 uterus and adnexa. In the same way the mammary glands are 

 stimulated to secrete milk, by an internal secretion derived from 

 the foetus, and lactation may be obtained by injecting an extract 

 into the virgin animal. One of the individuals of a " Siamese 

 twins " was recently delivered of a child, and both started lactating. 



