352 



Transmission. Infection has been effected by 

 means of a rat flea (P. fasciatus) and, it is stated, by the 

 rat louse (H aematopinus spinulosus) also. With the 

 louse we have experimented, but always in vain. 

 Prowazek, who, however, also failed to transmit 

 infection by the louse, describes a complex develop- 

 mental cycle in the gut of the louse. 



(i) Fertilisation of a female (thick form, with 

 spherical nucleus) by a male trypanosome (slender, with 

 a slender nucleus) occurs. (2) Formation of an 

 ookinet with a single spherical nucleus. (3) Develop- 

 ment of a trypanosome from this ;* as the flagellum now 



Fig. 109. T. lewisi : shewing rosette formation as the re suit oj division 



appears at the same end as the blepharoplast, this is 

 taken to be the anterior end of the trypanosome ; later, 

 the blepharoplast moves away to the opposite (pos- 

 terior) end, viz., that of its normal position. Besides 

 this cycle, the trypanosomes are also said to assume 

 gregarine-like non-flagellate forms, which penetrate 

 between the epithelial cells. How far these forms 

 belong to T. lewisi and how far to possible natural 

 trypanosomes of-the louse's gut, remains to be seen. 



Cultivation. (Novy and MacNeal). Mix agar, 

 melted and cooled to 50 C., with defibrinated rabbit's 



