Ill 



the same substance to be a food in some cases and a fat 

 in others according to the concentration and conditi 

 poison may accelerate the vital processes, may retard tl 

 may stop them. 



It is now firmly believed that the so-called vital proc 

 largely. The digestion of starch 



which o 



sugar 



standing of the 



advance in chemistry and physics offers a new basis for an ad- 

 vance in physiology so that now considerable attention is being 

 paid to the separate vital processes as chemical reactions rather 

 than to the activity of the organism as a whole, which is of course 

 much more complicated. Gradually more and more of the vital 



Thus the effect of poisons upon the digestion 



We may think of a chemical reaction between two substances 



■hich results in the formation of a third substance different from 

 :he original ones. A poison, then, is a foreign body whose pres- 

 alters the rate of reaction between two others. Modern re- 

 in has shown that any third substance more or less alters the 

 of a given reaction. In this sense every substance may un- 

 ome conditions be a poison. To understand why a substance 

 ison apparently involves a knowledge of why any third body 

 in influence, great or small as it may be. Any number of 

 ■thetical questions might be asked here but it is evident that 



Before modern research had revealed the important part taken 

 ■by electrical energy in chemical changes numerous attempts were 

 made to correlate the poisoning capacity of the elements with 

 their physical and chemical properties as then known. Thus com- 

 pounds containing the heavy metals, mercury, copper, lead, etc., 

 were found to be more poison than those containing the lighter 



