Stimulated by the statements of Manson and Ross that kala azar probably existed in America, Samuel T. Darling began the search for Leishman-Donovan bodies in smears from the spleen, liver and bone marrow in all cases of splenomegaly that were examined post mortem at Ancon Hospital, Canal Zone, Panama. In 1905 Darling1 encountered a patient with splenomegaly, emaciation, irregular fever, leukemia and anemia. The essential pathologic features found post mortem on this patient were "the invasion of endothelial cells in the smaller lymph and blood vessels and capillaries by enormous numbers of a small encapsulated microorganism causing necrosis of the liver, with cirrhosis, splenomegaly, pseudogranulomas of the lungs, small and large intestines with ulceration of the latter, and necrosis of lymph nodes draining the infected viscera." The organism was round to oval and measured from 1 to 4 microns in diameter. After staining, the organism was seen to possess