102 THE ANIMAL PARASITES OF MAN 



(2) Reference has been made on p. 93 to the experiments of 

 Gonder, who showed that a strain of T. lewisi rendered resistant to 

 arsenophenylglycin lost its resistance after passage through the rat 

 louse. This is in marked contrast with the retention of drug resistance 

 during passage by inoculation from rat to rat. 



(3) T. lewisi from the blood of a rat when transferred to a snake 

 seems largely to disappear, as very few flagellates are seen. When 

 blood from the snake is inoculated into a clean rat, then trypano- 

 somes reappear in the rat, but they are not all like those originally 

 inoculated. It seems certain that, in such a case, changes in form 

 and virulence of the trypanosome have occurred. Similar experiments 

 were made with T. brucei from rats to adders and other animals and 

 back to rats. Changes in the form and virulence of T. brucei occurred. 



These interesting experiments were performed by Wendelstadt and 

 Fellmer. 1 



Genus. Herpetomonas, Saville K^nt, 1881. 



Herpetomonas is a generic name for certain flagellates possessing 

 a vermiform or snake-like body, a nucleus placed approximately cen- 

 trally, and a blepharoplast (kinetic nucleus) near the flagellar end. 

 There is no undulating membrane (fig. 49, a). The organisms in- 

 cluded in this genus certainly possess one flagellum, while according 

 to Prowazek (1904) Herpetomonas muscce-domesticce, the type species, 

 possesses two flagella united by a membrane. Patton, 2 Porter 3 and 

 others affirm, however, that the biflagellate character of H. mnscce- 

 domesticce (from the gut of the house-fly) is merely due to precocious 

 division. The matter is further complicated by the generic name 

 Leptomonas, given by Kent in 1881, to an uniflagellate organism found 

 by Biitschli in the intestine of the Nematode worm, Trilobus gracilis. 

 This parasite, Leptomonas butschlii, has not yet been completely 

 studied. Until these controversial points relating to the identity or 

 separation of Herpetomonas and Leptomonas have been satisfactorily 

 settled, we may retain the better known name Herpetomonas for such 

 uniflagellate, vermiform organisms. However, the name Leptomonas, 

 having been used by Kent two pages earlier in his book (" Manual of 

 the Infusoria ") than Herpetomonas, would have priority if the two 

 generic names were ultimately shown to be synonymous. 



A full discussion of these interesting and important flagellates 

 hardly comes within the purview of the present work ; brief mention 

 can only be given here to certain species. 



The Herpetomonads occur principally in the digestive tracts of 

 insects, such as Diptera and Hemiptera. They are also known in the 



1 Zeitschr. f. Immunitatsforschung, iv, p. 422 (1909), and v, p. 337 (1910). 



2 Arch.f. Protist., xiii, p. i. 3 Parasitology, ii, p. 367. 



