528 



Kala-Azar 



are concerned. Any associated growing bacteria quickly destroy 

 Leishmania donovani. 



Under conditions of cultivation the appearance of the organism 

 undergoes a complete change. It ehlarges, the nucleus increases 

 greatly in size, and a pink vacuole appears near the blepharoplast. 

 In . the course of twenty-four to forty-eight hours the organism 

 elongates, the blepharoplast moves to one end, and from the vacuole 

 near it a flagellum is developed, and the organism becomes in about 

 ninety-six hours a flagellate protozoan resembling herpetomonas. 

 It now measures about 20 fi. in length and 3 to 4 m in breadth, its 

 whip or flagellum measuring about 3 n additional. It is also motile, 

 and, like the trypanosomes, swims with the flagellum anteriorly. 

 There is no undulating membrane. 



This may be regarded as the perfect or adult form of the organ- 

 ism. It multiplies by a peculiar mode of division first observed by 



Fig. 218. — ^Leishmania donovani. Flagellated forms obtained in pure cultures 



(Leishman). 



Leishman. Chromatin granules, a larger and a smaller, appear 

 in the protoplasm in pairs, after which, through unequal longitudinal 

 cleavage, long, slender, almost hair-like individuals, containing one 

 of the pairs of chromatin granules, are separated. These were 

 serpentine at first, but later, as they grew larger, a flagellum was 

 thrust out at one end. 



Distribution. — The Leishman-Donovan body is widely distrib- 

 uted throughout the body of the patients suffering from kala-azar. 

 It occurs in great numbers in the cells of the spleen, of the liver, of 

 the bone-marrow, and in the ulcerations of the mucous membranes 

 and skin. In the peripheral blood they are few and only in the leuko- 

 cytes. They are always intracellular, or when in the circulating 

 blood may be found in indefinite albuminous masses, probably de- 

 stroyed cells. The number in a cell varies up to several hundred, 

 such great aggregations only being found in the pecuUar large cells 

 of the spleen. 



Lesions. — The splenomegaly is the most striking lesion. The 

 change by which the enlargement is effected is not specific. The 



