ceptions encountered were so numerous as to make a satisfactory 

 explanation impossible. 



According to the modern view chemical action is largely an 

 affair between small particles called ions. Each ion carries an 

 electrical charge. Some ions carry a negative charge and others 

 carry a positive one. Some ions hold their charges much more 

 tenaciously than others. When an ion loses its charge or gains an 

 additional one it suffers a change and likewise the ion from which 

 it gained the charge or to which it lost one. Now we may think 

 of a living organism as an association of ions between the mem- 

 bers of which there is a constant interchange of electricity. This 

 interchange is outwardly manifest as the so-called vital processes. 

 As long as the interchange remains in natural equilibrium the 

 organism lives, but when this equilibrium is disturbed the organ- 

 ism is poisoned and death is a matter of the degree of the dis- 



example, approaches this association of ions (our living organism) 

 and comes within the sphere of influence. It is an experimental 

 fact that the mercury ion does not hold its charge very firmly, 

 so that some ion member of our association steals the charge 

 carried by the mercury ion. The electrical equilibrium previously 

 existing in the organism is thus disturbed by the additional charge 

 and perhaps a total readjustment of the electrical relations occurs 

 — the organism is poisoned. Now suppose some other ion in- 

 stead of the mercury, for example a sodium ion, reaches the 

 sphere of influence of our organism. Since the sodium ion 

 holds its charge too firmly to lose it, the chemical relations of 

 the organism remain undisturbed — the sodium is not poison. 

 This is essentially the latest theory of the real nature of poison- 

 ing. Those substances are most poison which hold their charges 

 least firmly. This theory was advanced in 1904 and has been 

 supported by two subsequent investigations by different men. 



During the past six months a test of the theory has been 

 made in the laboratory of the Garden. The digestion of fat was 

 selected as the chemical reaction upon which the effect of a 

 series of poisonous metals was tried. This reaction had never 

 been tested and it proved to be more favorable for the pur- 



