54 SOME MINUTE ANIMAL PARASITES 



interest, inasmuch as certain of its members (or forms 

 very nearly allied thereto) are responsible for the 

 diseases known as " Kala-azar," " Oriental sore," or 

 "Delhi boil," and "infantile splenomegaly" of the 

 Mediterranean littoral. The parasites of Kala-azar 

 and Delhi boil are generally placed in a separate 

 genus, Leishmania. 



Here again a danger arises from generalizing on 

 a few cases the random sampling of the logician. 

 Because some herpetomonads cause foul diseases, and 

 are spread by insects, it by no means follows that all 

 herpetomonads, parasitic in all biting insects, do the 

 same. Nor is there the slightest evidence whatever 

 to warrant the connexion of the genus Herpetomonas 

 with that of Trypanosoma, because it may occur in 

 a biting insect. Recently, a most careful investiga- 

 tion of lice frequenting the human body has been 

 made, and has resulted in the discovery of a typical 

 Herpetomonas. But the flagellate, known as Herpeto- 

 monas pediculi, is a parasite of the insect, and has no 

 harmful effect of any sort on man. 



In order to prevent the possibility of contamination 

 from outside sources, the lice were bred and fed on 

 the body of the investigator, and the young lice 

 became infected by swallowing cysts in the excre- 

 ment of the older ones. In the faecal matter there 

 are minute, oval bodies (Fig. 12, A), resembling 

 those of Crithidia. They contain a nucleus and 

 blepharoplast, and have a varnish-like cyst wall. 

 These are the post-flagellates. Swallowed with 

 faeces by other lice, the cysts become softened, the 

 parasites grow and begin to elongate (Fig. 12, B-D) 



