CHAPTER XXL 



THE RELATION OF SAPROPHYTIC TO PATHOGENIC ORGANISMS.^ 



There is hardly any question which to the pathologist and 

 sanitary officer can be of greater importance than the relation 

 of saprophytic to pathogenic or parasitic organisms. To the 

 pathologist the life-history of a micro-organism, outside and 

 within the animal body, must ever remain an important field 

 of inquiry ; to the sanitary officer all conditions affecting the 

 life and death of those organisms which produce, or at least 

 are intimately bound up with, infectious diseases, such as the 

 distribution and growth of these micro-organisms outside the 

 animal body, the agencies which affect it in a favourable and 

 unfavourable sense, are the points which he has particularly 

 to consider in dealing with the spread and prevention of 

 infectious maladies. Now, it is known of many micro- 

 organisms, both those that are associated with putrefactive 

 processes as well as those that are bound up with infectious 

 disease, that temperature, the character of the medium in 

 which they grow, presence and absence of certain chemical 

 compounds, &c., are capable of materially affecting them. I 

 need not for this purpose enumerate all that is known already 



^ Part of this chapter is copied from an interim report by myself to 

 the Medical Officer of the Local Government Board, 1884. 



