574 



Kala-Azar 



ulceration of the intestines, and necrosis of the lymph-nodes 

 draining the injected viscera. The lesions seemed to depend 

 upon the invasion of the endothelial cells of the smaller 

 lymph- and blood-vessels by enormous numbers of a small 

 encapsulated micro-organism. 



The organism is small, round or oval in shape, and meas- 

 ures i to 4 ft in diameter. It possesses a polymorphous, 



Fig. 199. Histoplasma capsulatum. Mononuclear cells from the 

 lung containing many parasites (Darling). (Samuel T. Darling in 

 "Journal of Experimental Medicine.") 



chromatin nucleus, basophilic cytoplasm, and achromatic 

 spaces all enclosed within an achromatic refractile capsule. 

 The micro-organism differs from the Leishman-Donovan 

 body of kala-azar in the form and arrangement of its chro- 

 matin nucleus and in not possessing a chromatin rod. The 

 distribution of the parasite in the body is accomplished by 

 the invasion of the contiguous endothelial cells of the smaller 



