354 FAMILY: TRYPANOSOMID^ 



while it still multiplied at 10° C, whereas L. donovani did not. L. cteno- 

 cephali showed a greater tendency to grow in clumps with the fiagella 

 internally directed, and it was generally more active than L. donovani. 

 The fully-grown flagellates of L. donovani varied in length from 9 to 12-5 

 microns, with fiagella 7-5 to 15-3 microns long. The corresponding stages 

 of L. ctenocephali measured 11 to 16-8 microns, with fiagella 7-3 to 21 

 microns in length. In the case of L. ctenocephali, the long forms fre- 

 quently had the aflagellar end extremely attenuated or ribbon-like, while 

 spiral twisting of this part of the body was common. In L. donovani the 

 nucleus was centrally situated, with the kinetoplast near the anterior end 



Fig. 16.5. — Leptomonas pulicis of the Human Flea [Fulex irritans). (Original). 

 A cluster of flagellates from a culture in N.N.N, medium ( x 2,000). 



of the body, while in L, ctenocephali the nucleus was definitely in front 

 of the middle of the body and the kinetoplast was near it. Chatton (1919) 

 had already drawn attention to the long, acicular forms which occurred 

 in cultures of L. ctenocephali, and which were absent from cultures of 

 L. donovani. Drbohlav (1925) hasshownthat dog fleas may be infected with 

 L. ctenocephali by injecting them per rectum with cultures, or by allowing 

 them to feed on cultures through a membrane. The cultures of L. pulicis 

 of the human flea studied by the writer (1912c) are very similar (Fig. 165). 

 Laveran and Franchini (1919, 1920) claim to have produced a 

 generalized infection of mice and guinea-pigs by inoculating them with 



