1904] The Chemical Regulation of the Secretory Process. 321 



presence of the products of inversion of lactose in the blood. This 

 was found not to be the case. Subcutaneous injection of galactose 

 for several days was not followed by any appearance of lactase in the 

 pancreas or its juice. Nor was the appearance of lactase due to the 

 increased production of this ferment in the mucous membrane, and its 

 escape into the blood. Injection of an extract of mucous membrane 

 rich in lactase, repeated several days in succession, was not followed 

 by any appearance of lactase in the pancreas. Injection of lactose 

 into the duodenum, and the subsequent injection of secretin after an 

 interval of 1 hour, was inefficacious in causing the appearance of 

 lactase in the pancreatic juice. For the production of lactase in the 

 pancreas, or its juice, it is therefore necessary that lactose should act 

 on the intestinal mucous membrane for some time. The reaction is a 

 slow one, like the adaptation in Vasilieff's experiments, and is 

 certainly not due to the stimulation of certain nerve endings in the 

 mucous membrane by the lactose. 



The problem was somewhat similar to that presented by the 

 action of acid in the duodenum, since this introduced into the 

 duodenum produces secretion of juice, whereas, when introduced 

 into the blood stream, it has no effect whatever on the pancreas. 

 The question suggested itself whether, under the influence of 

 lactose, a special secretin was formed in the intestinal mucous 

 membrane which, on access to general circulation, evoked the forma- 

 tion and secretion of lactase by the pancreas. Secretin was there- 

 fore made in the usual way (i.e., acidification, boiling, neutralisation,, 

 and filtering) from the mucous membrane of milk-fed dogs. The 

 secretion evoked by the injection of this liquid resembled that 

 obtained from the injection of ordinary secretin, and contained no 

 lactase. 



Yet it was evident from the results already obtained that lactose 

 must act on the pancreas through the mucous membrane of the 

 intestine. An extract was therefore made from the mucous membrane 

 of the whole small intestine of a milk-fed dog. This was filtered 

 through muslin, and about 10 c.c. injected subcutaneously into a 

 biscuit-fed dog once a day for three days. The dog was then 

 anaesthetised, a cannula placed in its pancreatic duct, and ordinary 

 secretin injected. A flow of pancreatic juice was obtained, and this 

 juice was found to contain lactase. This experiment was performed 

 eight times, and in each case the juice obtained from a biscuit-fed dog 

 which had been injected with an extract of the mucous membrane of a 

 milk-fed dog contained lactase. 



Here then at last we have some glimpse into the mechanism of the 

 adaptation of the pancreas to the nature of the food. As the result of 

 injection of lactose some substance which we may call x is produced in 

 the mucous membrane of the small intestine. This substance is carried. 



