120 THE WORK OF THE DIGESTIVE GLANDS. 



the fact that in the early hours after a meal of flesh a very vigorous 

 secretion of gastric juice takes place, the acid of which appears to be at 

 the same time the chief exciter of pancreatic flow. 



Consequently, a non-nutrient substance, namely the acid, has proved 

 itself to be the strongest excitant of the neuro-secretory apparatus of 

 the pancreas. This does not, however, preclude the possibility that there 

 may also be other exciters, either identical with those for the gastiic 

 glands, or different therefrom, since the field of action is wider in the 

 case of the ferments of the pancreas. Hence the natural question 

 arises whether starch and fat may not also be exciters of the pancreas, 

 for, as we know, the gland has special relations to these substances. So 

 far as our experiments go, we were unable to prove an exciting effect 

 on the part of starch. Solutions of starch of varying concentration 

 expelled the juice no more energetically than water alone. The 

 question, however, requires still further investigation, for it is quite 

 possible that the minutiae of the requisite conditions for the starch 

 effect may for the time being have escaped our observation. It may, 

 for instance, happen here, as in the case of gastric juice, that the starch 

 exercises only a trophic influence that is to say, augments the quantity 

 of the ferment without increasing the total quantity of juice. Some 

 experiments of Dr. Walther furnish a basis of fact for these hypotheses. 

 When he fed a dog with bread, the pancreatic fluid possessed a much 

 stronger amylolytic action than the juice obtained at a corresponding 

 period, and with the same rate of flow, after a meal of flesh. It is par- 

 ticularly interesting that in the same specimens of juice the fat-splitting 

 ferment behaved in just the opposite way the flesh juice revealed a 

 greater, the bread juice a lesser degree of fat-splitting action. 



Finally, the possibility is not excluded that the progress of starch 

 digestion may be dependent on some other condition for example, the 

 continued production of lactic acid from the carbohydrate constituents 

 of the food. Possibly this is the explanation of the chemico-physiological 

 fact in question, the meaning and importance of which have as yet been 

 but little cleared up. Science has not attempted, and could not up to 

 the present venture, to reproduce a synthesis of real digestion that is 

 to say, to combine the often conflicting interests of the different food- 

 stuffs among themselves with those of the digestive canal and of the 

 organism as a whole. Here I beg to remind you of the relationships of 

 fat to gastric digestion, and of the probable importance of the acid 

 effect. 



The experiments dealing with the influence of fat upon the pancreatic 

 gland yielded much more positive results and were much simpler. In- 

 deed, the mere comparison of known facts made it very probable that fat 

 is an independent exciter of the pancreas. Fat restrains the secretion 



