LEISHMANIA TROPICA 429 



allied to leishmania, is C ry ptococcus farcinimosus , the cause of lymphangitis 

 of horses (Plate III., p. 394). 



The occurrence of flagellate forms of Leishmania tropica in oriental sore 

 has been referred to above (p. 425). The writer has never seen such forms, 

 though not infrequently fibres and filaments amongst the debris, especially 

 if associated with parasites, may give the appearance of flagella. 



CULTURE. — Leishmania tropica, which grows in artificial media as readily 

 as L. donovani, was first successfully cultivated by Nicolle (19086) in Tunis, 

 Row (1909), in India, was also successful, as also were Markham Carter 

 (1909), Marzinowsky (1909), and the writer (1911a). Pedroso (1910) 

 appears to have first obtained culture of L. tropica from the South American 

 disease. The writer (19126) also cultivated the organism from a case of 

 South American origin. The cultures of L. tropica behave like those of 

 L. donovani, the most suitable temperature for growth varying from 

 22° to 25° C. It is possible that L. tropica grows more vigorously than 

 L. donovani, but variation in individual strains is often considerable. In 

 the writer's experience, certain strains of L. tropica grow very readily and 

 others with greater difficulty, especially in the first subculture. Similarly, 

 it sometimes appears that a slightly higher temperature is more favourable, 

 but there is no uniformity in this. Giugni (1914a), for instance, claims 

 that the optimum temperature for L. tropica is 28° to 29° C, while that 

 for L. donovani is 21° to 22° C. The writer has kept many strains of both 

 L. tropica and L. donovani growing for long periods at a temperature of 24°C. 

 Nicolle (1925) reports having maintained a strain of L. tropica in culture 

 for over fifteen years, during which it has passed through 384 sub-cultures. 



Morphologically, the forms which appear in cultures of L. tropica are 

 indistinguishable from those of L. donovani (Fig. 190). Some have main- 

 tained, as Row (1909) has done, that L. tropica produces larger forms 

 than L. donovani, but the size of the flagellates varies with the age of the 

 culture, and also with different batches of medium, which can never be 

 prepared with absolutely uniform composition. Such a variety of forms 

 occurs in the cultures, and these in such varying proportions, that com- 

 parison between different cultures is exceedingly difficult to make. 



To obtain cultures from an oriental sore, it is necessary to secure 

 material free from bacteria. In the ulcerating varieties, this can only be 

 done by carefully sterilizing the skin at the edge of the ulcer with iodine 

 or other antiseptic, making a puncture with a needle or sharp knife, and 

 drawing off material by means of a sterile pipette. The material in the 

 pipette is then blown into the liquid at the bottom of a tube of N.N.N. 

 medium. Flagellates are to be detected in the tubes in from three days 

 to three weeks, according to the number of organisms introduced. 



