234 PHYSIOLOGY OF ALIMENTATION. 



ficient, it means a lack of acid in the duodenum, and this 

 in turn means a deficient secretion of pancreatic juice. 



7. On the " Adaptation " of the Digestive Glands to the 

 Character of the Food. The opinion that the secretions 

 of the various digestive glands "adapt" themselves to the 

 character of the food consumed by the individual, that, in 

 other words, each diet calls forth a particular kind of diges- 

 tive secretion, has been expressed from time to time by various 

 authors. With all of them, however, this opinion has rested 

 more upon philosophical speculations than upon experimental 

 facts. 



The first to attempt to give experimental foundation to such 

 an idea was PAWLOW, and with him ORIGIN and WALTHER. 

 But the experiments which these investigators have detailed 

 in support of their belief, and which have been touched upon 

 in the preceding pages, have been so energetically attacked 

 by others that, at the best, they can be looked upon as by 

 no means convincing. 



With all the more pleasure, therefore, can we proceed to a 

 discussion of the experiments of WEINLAND,* which indicate 

 without question that one digestive gland at least, the pan- 

 creas, can and does "adapt" itself to a particular diet. 

 WEINLAND'S experiments show that the pancreas and pre- 

 sumably, therefore, the pancreatic juice of the adult dog, 

 which normally contain little or no lactase, come to con- 

 tain this enzyme in large amounts if the dog is fed milk- 

 sugar, or a diet containing milk-sugar, such as milk. This 

 means that the pancreas and pancreatic juice, which in the 

 adult dog normally contain little or no ferment which can act 

 upon lactose and split this into galactose and dextrose, de- 

 velop this sugar-splitting ferment in response to certain diets. 



What has been said can be best illustrated by introducing 

 one of WEINLAND'S experiments. An adult dog was kept on 

 an abundant diet, but free from milk-sugar, for five days; 



I WEINLAND: Zeitschr. f. Biol., 1899, XXXVIII, p. 16; ibid., 1899, , 

 XXXVIII, p. 607; ibid., 1900, XL, p. 386. V 



