OF POISONS. 



investigate are those which give rise to certain forms 

 of disease which spread from person to person. Many 

 poisons of this class, as compared with non-living 

 poisonous agents, act very slowly, and when they 

 destroy life, do so, not by their immediate action 

 upon tissue or living matter, but by their indirect in- 

 fluence upon the physiological changes going on in 

 various tissues and organs. Many of these poisons 

 are indeed uncertain in their action, and are for the 

 most part fatal to a very small percentage of those 

 attacked. They not unfrequently cause serious struc- 

 tural damage in consequence of which the organism 

 becomes predisposed to certain forms of disease ; and 

 oftentimes, although the individual invaded escapes 

 with his life, some delicate organ is irreparably injured 

 by the changes produced by the action of the poisonous 

 material, and death follows after a varying interval of 

 time, but long before the ordinary period of life has 

 been reached. 



These poisons not only seriously derange the healthy 

 functions, but having entered the body they multiply 

 many million fold. They are living, and increase as 

 living particles alone increase. They grow, they 

 feed upon the nutrient juices of the organism and 

 upon the tissues, and in some cases flourish at their 

 expense and destroy them. The poison when it 

 enters may be so infinitesimal in quantity, that it 

 can neither be measured nor weighed, nor under 

 ordinary circumstances seen ; but having gained access 



