318 



Dr. W. M. Bayliss and Prof. E. H. Starling. [Mar. 21, 



quantity of acid gastric contents to enter the duodenum. By this 

 double mechanism, which is partly nervous, partly chemical, it is pro- 

 vided that the acid contents of the stomach shall pass on into the gut 

 only in such quantities as can be dealt with by the secretory mechanisms 

 of the intestine. 



One more chain in the link of adaptive reactions may be briefly 

 mentioned. The pancreatic juice, as secreted, contains only a weak 

 proteolytic ferment. But it contains also trypsinogen. As soon as 

 this juice enters the gut it causes a profuse secretion of intestinal juice. 

 This latter contains another ferment, enterokinase, which acts on the 

 trypsinogen, converting it into a body trypsin, one of the most active 

 proteolytic ferments with which we are acquainted. 



So far we have dealt only with the correlation of the activities of 

 the cells lining the intestinal tube with those forming the masses of the 

 pancreas and liver, and have seen that a very large part in this correla- 

 tion is played by a chemical substance which acts, so to speak, as a 

 chemical messenger between these various organs. A striking feature, 

 however, of the pancreas is its alleged power of adapting its secretion 

 to the nature of the food taken in by the animal. It has been stated 

 by Pawlow that according as the food consists chiefly of proteids, 

 carbohydrates, or fats, so do we find a relative preponderance of the 

 ferments acting respectively on each of these three classes of foods. 

 The evidence on which this statement is based, although lending to it 

 considerable support, is not absolutely convincing. Vasilieff* examined 

 the pancreatic juice of dogs which were fed on meat, or bread and milk 

 alternately for periods extending over several weeks for each kind of 

 diet. This observer found that the transition from bread and milk 

 diet to a meat diet caused a rapid rise in the proteolytic power of 

 the juice, which reached its maximum after several days of meat 

 feeding. A return to a diet of bread and milk caused a slower fall 

 in the proteolytic power of the juice, but a rise in the amylolytic 

 power. Similar results were obtained by another pupil of Pawlow — 

 Jablonskyf — who also extended his observations to the fat-splitting 

 ferment. At the time that these observations were made the function 

 of enterokinase was unknown, and it is therefore impossible to say 

 what proportion of the trypsinogen of the juice secreted in these 

 experiments had been converted into trypsin by the small amount of 

 intestinal mucous membrane at the mouth of the duct. While, there- 

 fore, we are unable to ascribe much importance to the results as regards 

 the proteolytic power of the juice, there seems no reason to doubt 

 the results obtained by these workers as regards the starch-digesting 

 power of the juice. In 1899 Walther| made a series of observations 



* ' Archives des Sciences Biologiques,' St. Petersburg, 1893. 



f Ibid., 1896. 



X Ibid., 1899, vol. 7, p. 1. 



