Histoplasmosis 



535 



The micro-organism differs from the Leishman-Donovan body 

 of kala-azar in the form and arrangement of its chromatin nucleus 

 and in not possessing a chromatin rod. The distribution of the 

 parasite in the body is accomplished by the invasion of the con- 

 tiguous endothelial cells of the smaller blood- and lymph-vessels 

 and capillaries, and by the infection of distant regions by the dis- 

 lodgment of infected endothelial cells and their transportation 



Fig. 222. — Histoplasma capsulatum. Mononuclear cells from the lung con- 

 taining many parasites (Darling). (Samuel T. Darling in "Journal of Experi- 

 mental Medicine. ") 



thither by the blood- and lymph-stream. Thus the skin, intestinal, 

 and pulmonary nodules may be due to secondary distribution of 

 the parasite. The micro-organism apparently lives for a con- 

 siderable period of time in the tissues, because in the older areas of 

 necrosis there are myriads of parasites all staining well. 



The mode of infection and portal of entry are unknown. The 

 parasite has neither been cultivated nor transmitted by inoculation. 



Believing it to be a new parasite, DarUng has suggested that it 

 be called Histoplasma capsulatum. 



