328 



THE ANIMAL PARASITES OF MAN 



worms obtained, i.e., about 4 per cent., thus corresponding to the infec- 

 tion of the fleas. The development in the flea probably begins in the 

 pupal stage, the eggs being ingested by the older flea larvae. The larva 

 is 0*31 by 0*25 mm.; tail 0*8 mm., scolex 0*075 by 0*09 mm., suckers, 

 0*055 mm. in diameter. Microscopically it shows (i) externally 

 a radially striated layer resembling cuticle, (2) a layer of columnar cells, 

 (3) parenchymatous layer continuous with the tail, (4) fibrous layer 

 around the small caudal vesicle, then the parenchymatous scolex at 

 the bottom of the secondary cavity. 



Nicoll and Minchin (loc. cit.) found a cysticercoid J in the rat flea 

 Ceratophyllus fasciatus which was probably that of Hymenolepis murina. 

 Body 0*16 mm., tail 0*19 mm., scolex 0-096 mm. in diameter. Ros- 

 tellum has twenty-three spines in a single row. Length 0*017 mm., 

 handle 0*01 mm., guard 0*007 mrn -> prong 0*007 mm - Sucker 0*042 mm. 

 Although this cycle, then, for H. murina also exists, it is not probable 

 that rats (or man in the case of H. nana if this be considered distinct) 

 infect themselves in this way, as they hardly 

 ingest all the necessary fleas to account for the 

 massive infection which frequently exists in 

 rats (and man), so that Grassi's cycle holds 

 good as the predominant method. Xenopsylla 

 cheopis has also been found by Johnston to 

 harbour both cysticercoids in Australia. 



Hymenolepis lanceolata, Bloch, 1782. 



Syn. : Tcenia lanceolata, Bloch, 1782; Drepanidotcpnia 

 lanceolata, Railliet, 1892. 



The parasite measures 30 to 130 mm. in 

 length and 5 to 18 mm. in breadth ; the 

 head is globular and very small ; the 



rzc.ssm. 



FIG. 232. Hymenolepis 

 laneeolata. Natural size. 

 (After Goeze.) To the 

 right above, two hooks. 

 1 20/1. (After Krabbe.) 



FIG. 233. Hymenolepis lanceolata : diagram of 

 female genilalia. ov., ovary; ovd., oviduct ; rec. sem,, 

 receptaculum seminis ; s.g., shell gland; ut., uterus; 

 y.g., vitellarium. (After Wolff hiigel.) 



'A third cysticercoid resembling this, but without hooks, has also been found. 



