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THE PROTOZOA 



V. THE GENUS LEISHMANIA. 



This genus was founded by Ross to include two human parasites : 

 the so-called Leishman-Donovan bodies, cause of the disease 

 known in India as " Kala-azar " ; and Wright's bodies (L. tropica), 

 cause of boils known by various local names, but termed compre- 

 hensively " Oriental sore." To these a third species namely, 

 L. infantum has been added by Nicolle (570), causing a disease in 

 children in Tunis, Algeria, and Italy, and found also in dogs, which 

 are regarded by Nicolle as the primary host of the parasite and the 

 source of the infection in human beings. In all cases the type of 

 parasite found in the vertebrate host is very uniform (Fig. 138) 

 small bodies, usually rounded or oval, contained within cells and 



Fia. 138. Leishmania donovani in cells. A, A macrophage ; B and 0, endothelial 

 cells containing the parasites (p.) ; n., nucleus of the infected cell. After 

 Christophers. 



multiplying by fission (Fig. 139). Each parasite possesses two 

 distinct nuclear bodies, which the development shows to be a tropho- 

 nucleus and a kinetonucleus respectively. The cells which harbour 

 the parasite are mainly, if not exclusively, of two classes namely, 

 leucocytes and endothelial cells ; the latter become greatly hyper- 

 trophied, forming the so-called " macrophages " (Fig. 138, A), which 

 may contain 150 to 200 parasites at a time. L, donovani was 

 believed originally to occur also in red blood-corpuscles, and was 

 first described as a species of the genus Piroplasma (p. 379). The 

 balance of evidence, however, is against their occurrence in the 

 h?ematids. If set free by the disintegration of their host-cell, they 



