There are, however, differences between the Indian and infantile kala-azars, in addition to the ages of the patients affected, thus: (_a_) As regards cultures, it is found that _L. infantum_ is readily grown on the Novy-MacNeal-Nicolle (“N.N.N.”) medium (saline blood-agar), and that sub-cultures are easily obtained; in citrated blood _L. infantum_ grows with difficulty. The reverse is the case with regard to culture media for _L. donovani_, which grows with difficulty on the N.N.N. medium, but relatively easily in citrated splenic blood. (_b_) Considering inoculability into experimental animals, it is found that _L. donovani_ is inoculated generally with some difficulty into white rats, white mice and monkeys, and with greater difficulty into dogs, while _L. infantum_ can be inoculated into several experimental animals, especially into dogs and monkeys, with ease. (_c_) At present _L. donovani_ is not known to occur spontaneously in animals, but _L. infantum_ is found naturally in dogs in the Mediterranean region, and the disease in dogs is often referred to as canine kala-azar. Kittens have occasionally been found infected. However, these differences must not be emphasized too much. The material for cultivation is obtained from punctures of spleen, liver or bone-marrow of cases infected with _L. infantum_. It is not always easy, however, to infect from cultures, as the cultural flagellates inoculated into the body are often phagocytosed. Similarly, the material for animal inoculation is obtained from emulsions of infected spleen, liver or bone-marrow. Dogs and monkeys are easily inoculated with such material; Nicolle inoculates into the liver or the peritoneal cavity. Mice, white rats, guinea-pigs and rabbits only show slight infections after such inoculations. Dogs infected experimentally with infantile leishmaniasis may show either acute or chronic symptoms. The acute course occurs more often in young dogs, and is usually fatal in three to five months. The chronic course is found more commonly in older dogs, and may last seventeen to eighteen months. In acute forms there is irregular fever, progressive wasting, diarrhœa occasionally, motor disturbances involving the hind quarters, and the animal dies in a comatose condition. In the chronic form the animal may appear well, except for loss of weight. The parasites may be found in the internal organs of these experimental dogs, but are not numerous in the peripheral blood except at times of high fever. Experimental monkeys live about three months.