368 Leishmania, Herpetomonas, and Crithidia 
produced, one of which presents a nucleus in which the karyosome is not 
visible, but which contains the maternal blepharoplast, while the other para¬ 
site contains no blepharoplast but shows a nucleus with a karyosome (Plate 
XXI, fig. 7). This explains the appearance already minutely described by 
V isentini, and leads us to believe in the nuclear origin of the blepharoplast. 
The heteromorphous division above described is probably of significance 
in the life cycle of Leishmania. The development of a parasite which at first 
is apparently without a blepharoplast is an important phenomenon; I think 
that some forms of the parasite may represent resistant forms which are of 
use in the maintenance of the species and which are produced under special 
conditions. I base this deduction on the fact that I have most frequently 
met with these forms in the haematopoietic organs of dogs naturally infected 
with leishmaniasis which was running a chronic course. 
(b) Leishmania in artificial cultures. Rogers, who was the first to cultivate 
Leishmania donovani did so by adding citric acid or citrate of soda in the pro¬ 
portion of 10 per cent, to the spleen or liver juice of individuals affected with 
leishmaniasis (Indian virus); his experiments being confirmed by Leishman 
and Statham whilst Longo subsequently cultivated the Mediterranean Leish¬ 
mania. Nicolle, in 1907, cultivated the parasite in the Novy-McNeal medium, 
and, in 1908, in the Novy-McNeal-Nicolle medium. 
Row, in 1912, obtained the cultural development of Leishmania donovani 
(Indian virus) in a haemoglobinised saline solution and Yisentini used this 
medium for cultivating Leishmania infantum. Leishmania also develops in 
Bordet and Gengou’s medium, in human blood agar and in Jemma’s ascitic- 
agar medium. The temperature is of the highest importance in the cultural 
development of these parasites; they develop at a temperature of between 
18° C. and 25° C., with the best results at 20° C. to 22° C. 
After inoculation, from four to five days, on an average, are required 
before flagellate forms of T^eishmania appear in the culture fluid. This de¬ 
velopment may however be completed in a shorter period. Visentini and I 
once saw a few flagellates appear 48 hours after cultures on N.N.N. medium 
had been inoculated with the splenic juice of a dog intensely infected with 
leishmaniasis. After several days non-flagellated forms reappeared and we 
regard these post-flagellate forms as representing resistant stages. 
During the first hours after inoculation the young non-flagellate parasites 
resemble the forms seen in the blood (peripheral and from haemopoietic 
organs); gradually they become pear-shaped (Plate XXI, fig. 8) and the flagel¬ 
lum develops (Plate XXI, fig. 9). Such flagellate piriform parasites usually 
measure 8-12 p, in length by 2-3 /x in breadth. Besides the pear-shaped 
parasites there occur some elongated forms (Plate XXI, figs. 10, 11, 12), with 
a pointed front end from which the flagellum projects. Leishmania in cul¬ 
tures reproduces itself by simple longitudinal division and this leads to the 
formation of slender elongated parasites (Plate XXI, figs. 13, 14, 15). 
After some days, there appear flagellate parasites of large size which may 
