Formerly it was thought that there were differences in the three species of _Leishmania_ from the standpoint of growth on various culture media, _L. donovani_ not growing on N. N. N. medium while _L. infantum_ grew well on N. N. N. medium but not in citrated blood. It is now known that both species will grow on these two media. It is absolutely essential in culturing _L. donovani_ or _L. infantum_ that the blood agar or citrated blood be sterile, as any bacterial contamination prevents growth. With the parasite _L. tropica_, however, bacterial contamination does not inhibit development and statements have even been made that growth is favored by a staphylococcal symbiosis. _L. tropica_, it would seem, will develop into flagellated forms in cultures at 28°C. while it will be remembered that Rogers in his original experiments failed to obtain other than commencing signs of division at 27°C., 22°C. being the temperature necessary for the development of flagellate forms. _L. tropica_ from South American cutaneous leishmaniases seems to grow more luxuriantly on N. N. N. medium than does that of oriental sore of Asia and Africa. Giugni tried N. N. N. media made with human, rabbit and dog blood, respectively. The parasites grew well on dog and rabbit blood media but not on that made with human blood. He found growth best when he added salt in quantity from 5 to 9 grams per liter. When red corpuscles are laked in a medium the growth is less favorable. While differences in development on different culture media may obtain not only with different species but with different strains of the same species, it would appear that such variations cannot be utilized as a means of separating the three species. _Animal Inoculation._—With animal inoculations we formerly thought that the parasite of kala-azar could be differentiated from that of infantile leishmaniasis by the fact that dogs could not be infected with _L. donovani_, while they were susceptible to infections with _L. infantum_. Recently Donovan and Patton have successfully inoculated dogs with kala-azar splenic material. Patton found the parasites in the liver, spleen and lymphatic glands as well as bone marrow of the inoculated dogs. Consequently we cannot separate the two visceral leishmaniases from a standpoint of susceptibility of the dog. Monkeys are susceptible to both diseases. It is important to recognize the fact that animal inoculations, even with spleen-juice, rarely give rise to infection.