METHODS. 



combination with other properties ? Are all the constituents of a 

 particular fluid simultaneously poured out on the food, and does this 

 happen with every kind of food I hat gains entry to the digestive canal ? 

 Are the reagents subject to variations, and if so when, how and why 

 do such alterations appeal' ? Do these variations only concern the 

 composition of the fluid as a whole, or may the individual constituents 

 alter in different cases and in different directions according to the 

 requirements of the raw material ? How do the reagents vary with 

 augmented or diminished activity of the whole factory ? Is there not 

 a species of contest between the different constituents of the food, in 

 that one may require a special reagent the activity of which would 

 interfere with that of others on the remaining ingredients ? No 

 one can deny that these questions touch upon the vital facts of the 

 case. 



The mechanism of digestion cannot be presented in the abstract 

 manner which is current in the physiological teaching of the present 

 time. The differences and complexity of the reagents indicate that the 

 work of the digestive canal in every single case is elaborately contrived, 

 beautifully performed, and most carefully adapted to the task in hand. 

 If we reflect, we must (t priori admit that for each meal i.e., for 

 each set of materials to be dealt with a suitable combination of reagents 

 with special properties is produced. It is not, therefore, to be wondered 

 at that the subject of dietetics, apart from some general and empirical 

 principles, represents one of the most intricate sections of therapeutics. 

 Nor is it enough for the physiologist to have a knowledge of the 

 separate elements concerned in the process of digestion, that is to say, 

 the working of the individual agencies. He must, in order to fully 

 grasp his subject, include also within the sphere of his observation the 

 actual progress of digestion as a whole. This was recognised by many 

 previous investigators who attempted, and doubtless would have accom- 

 plished, the solution of the problem had it been of an easier description. 



A comprehensive knowledge of the processes of digestion may be 

 acquired in one of two ways either by determining in what state of 

 elaboration the raw material is to be found at each separate part of the 

 digestive canal this was the method of Brlicke, as well as of Ludwig 

 and his pupils or, on the other hand, by ascertaining the exact 

 quantity of the digestive fluids which is secreted for each individual 

 constituent of the food, as well as for the meal as a whole, how this 

 digestive fluid is provided, and when it is poured into the alimentary 

 canal. This method has been adopted by many investigators who have 

 studied the progress of the secretion of the various digestive juices. 



It is often said, and not without truth, that science advances by 

 stages determined by the results obtained from particular method?. 



