64 



DISEASES DUE TO PROTOZOA 



Tlie squamous epithelium is surrounded by desquamated epithelium. 

 Crusts are formed. The lymphatic and blood vessels in the deeper 

 layers are surrounded by lymphoid cells. There are vertical epithelial 

 columns extending deeply down with a few cell nests and isolated 

 masses of cell infiltration. 



It is essentially an infective granuloma. 



Hair, sweat glands, sebaceous glands and follicles are invaded and 

 destroyed by granular tissue. 



A case of Leishmaniasis from South America. (Photograph by R. McKay.) 

 (From \ht /ou7-nal of the London School of Tropical Medicine.) 



Polymorphonuclear cells do not predominate in the ulcers as in 

 pyogenic ulcerations, but the mononuclears do. 



SYMPTOMATOLOGY. 



The incubation period is from a few davs to a few months. 



During this period there is usually some irregular fever. 



Then several small spots appear, not unlike mosquito bites. These 

 become red, markedly indurated, increase in size, and the surface 

 becomes covered with scales. 



