under other auspices, both in this and in foreign countries. A survey 

 of the field of research in this direction shows that. three principal 

 methods of procedure have been followed. 



In the first case may be cited those investigations which have been 

 conducted by means of artificial digestion. Fortunately for science, 

 the various ferments which are active in digestion in the living animal 

 have been isolated and prepared in a reasonably pure state. By secur- 

 ing as nearly as possible the other conditions which obtain during 

 digestion in the living body, artificial digestion similar thereto can be 

 secured. Thus if food properly comminuted and kept, at the tempera- 

 ture of the stomach, in motion similar to that produced by the peri- 

 staltic action of the intestines, be treated by the proper digestive acids 

 and ferments, the chemical actions which occur are entirely similar to 

 those which take place in the living organ itself. Thus the ferments 

 which digest starch and sugar, those that act upon protein, and those 

 that act upon fats can be studied without the living organism. The 

 results which have been obtained by this method of investigation are 

 most valuable, and when the preservatives and coloring matters in 

 question are added, any changes which are produced, either in the 

 degree or in the rate of digestion, can be easily ascertained. 



In the second case the problem may be studied by experiments con- 

 ducted upon the lower animals, and from the results of these experi- 

 ments inferences may be drawn applicable to the human animal. This 

 line of experiment and investigation has also great merit. The animals 

 operated on are kept under close control. The amount of food which 

 they consume is easily ascertained. The excreta they produce are col- 

 lected, and a complete chemical control can be instituted in connection 

 with the digestive process. When preservatives and coloring matters 

 are added to the food of animals thus treated, any changes which take 

 place in the digestive processes or any lesions which are produced in 

 the organs of the body can be ascertained. This method of investiga- 

 tion also has the additional merit that at the end of the period of 

 observation the animal may be killed, and changes in its organs, which 

 were so slight as to produce no observable effects during life, may be 

 sought and discovered. Thus, minute or incipient lesions of the 

 digestive organs, or of the other organs of the body, are brought to 

 light which otherwise would escape notice. If the digestive processes 

 in the lower animals were exactly the same as those in the human ani- 

 mal this method of investigation would necessarily be accepted as final 

 and conclusive ; but each species of animal has its own peculiarities of 

 digestion, and, therefore, the results produced on one species of animal 

 by a certain course of treatment might not be secured with an animal 

 of a different species or genus. This fact has led investigators to under- 

 take a third kind of research, namely, experiments with the human 

 animal itself. 



