CHAPTER II 



Dissemination and the Prevention 

 OF Infection 



The protozoa of man's alimentary tract are com- 

 monly transmitted from the human carrier to a new 

 host by contamination of materials taken into the 

 mouth by secretions or excretions of the infected in- 

 dividual, in fact the commonness of these organisms 

 in man is a concrete illustration of the real uncleanli- 

 ness with which the human is still in contact, in spite 

 of vaunted sanitary procedures. This has been 

 particularly stressed by Boeck and Stiles (1923), and 

 by Dobell and O'Connor (1921). The incidence of 

 intestinal protozoa is a direct index of the swallowing 

 of fecal matter. 



Those which inhabit the mouth are probably trans- 

 mitted by kissing and by the placing of things in the 

 mouth which are contaminated with saliva from the 

 infected person. Ready passage of the mouth pro- 

 tozoa from one person to another is indicated by their 

 failure to encyst. 



Of those of the intestine, the encysting species find 

 this resistant phase necessary to survival of an in- 

 terval between passage, with excreta, from their 



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