BORIC ACID AND BORAX. 9 



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 temper- 

 ature 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 

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

 that act upon fats can be studied outside of 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, aiw changes which are produced, either in the 

 degree or in the rate or 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 upon are kept under close control. The amount of food 

 which they consume is easily ascertained. The- excreta they produce 

 are collected, and a complete chemical control can be instituted in 

 connection with the digestive process. When preservatives and color- 

 ing 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 investigation 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 proc- 

 esses in the lower animals were exactly the same as those in the human 

 animal, this method of investigation would necessarily be accepted as 

 final and conclusive; but each species of animal has its own peculiari- 

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

 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 un- 

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

 animal itself. 



This method of investigation also has advantages as well as m&ny 

 disadvantages. For the most part such investigations are carried out 

 upon volunteers, since no one could be forced to undergo any such 



