320 



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



amount of juice will, therefore, be measured by the stay and resistance 

 to digestion of the substance in the stomach rather than to any 

 direct nervous or other influence of the duodenal contents on the 

 pancreas. A repetition of Walther's experiments by Popielski,* 

 working independently, has in fact led the latter to deny altogether 

 the adaptation of the pancreatic juice to the nature of the food. 

 Popielski concludes from his experiments that variations in the juice 

 depend only on the intensity and duration of the stimulus, the 

 intensity of the stimulus determining the amount of enzymes, whilst 

 its duration determines the total quantity of juice. 



In the meantime the question had been attacked from another side. 

 It had been shown by Fischer and Niebelf as well as by PortierJ that 

 watery extracts of the pancreas of the cow, horse, and dog had no 

 influence on lactose. Weinland in 1899 confirmed these results so far 

 as concerns the pancreas of dogs on an ordinary diet free from milk. 

 On the other hand, he found that extracts of the pancreas of dogs, 

 which had been fed for several days on milk, sometimes with the 

 addition of lactose, invariably contained lactase in considerable 

 amount, and these results have been confirmed lately by Bainbridge 

 working in our laboratory. Here then we have a definite instance of 

 adaptation of the pancreas, the pancreatic juice or pancreatic extracts 

 of dogs on normal diet containing no lactase, while the administration 

 of lactose to these animals causes the appearance of lactase in both 

 cases. Since in this case we have to determine, not simply an increase 

 or diminution in the amounts of ferments always present in the 

 juice, but the presence or absence of a definite substance, this was 

 evidently the best starting point for an investigation of the mechanism 

 by which the pancreas can adapt itself to the nature of the food, 

 an investigation which has been carried out and completed by 

 Dr. Bainbridge. 



What are the limiting conditions 1 In the first place the reaction 

 is absolutely specific. Unless the animal is taking lactose in its diet 

 no lactase is ever found in the pancreas or in its secretion. The 

 pancreas of new-born animals, for instance, is quite free from lactase, 

 which, however, makes its appearance 2 or 3 days after birth as the 

 result of the milk diet. The production of lactase is not a direct 

 reaction of the pancreas to the presence of lactose in the blood, since 

 subcutaneous or intravenous injection of lactose does not cause the 

 appearance of lactase in the pancreas. The intestinal mucous mem- 

 brane of all animals, whether on a milk diet or not, contains lactase 

 and has an inverting action on lactose. It might be thought therefore 

 that the production of lactase by the pancreas was a reaction to the 



* ' Centralblatt f. Physiol ogie,' vol. 17, 1903. 



+ ' Sitzungsberichte der K. Preuss. Akad. d. Wiss.,' 1895, p. 73. 



Z 1 C. R. Soc. de Biologie,' 1898, p. 387. 



