234 



THE PATHOGENIC FLAGELLATES 



regarded as developed herpetomonas forms which have become 

 specially adapted for life in the blood, the undulating membrane 

 being a special reaction on the part of the organism to the conditions 

 in the blood. 



Fig. 92 



Types of undulating membranes. M, membrane, (After Calkins.) 



It is quite otherwise with the supposed genus leishmania in regard 

 to which every new observation tends to strengthen Rogers' ('05) view 

 that this organism of kala azar agrees with herpetomonas in all of 

 its generic diagnostic characters. Crithidia also rests upon differ- 

 ences of a very slight nature, but the primitive type of membrane at 

 the base of the flagellum is of positive diagnostic value and in most 

 cases it is sufficient to distinguish this genus from herpetomonas. 



In all forms the flagellum is well defined and of the characteristic 



