RICKETTSIA IN TISSUES 193 



Mountain spotted fever, so that we can state with assurance 

 that the bodies described as rickettsia in typhus lesions are 

 peculiar to typhus and are indistinguishable from rickettsia 

 as seen in the infected louse. 



In chicken-pox material recently provided by Dr. James 

 Denton perivascular accumulations of cells about the papil- 

 lary capillaries and vessels of the sub-papillary plexus bear a 

 resemblance to the lesions of typhus. The vascular lesions 

 seem to be limited to swelling and proliferation of the endo- 

 thelium without thrombosis. The changes in the epidermis 

 preceding and coincident with vesicle formations preclude 

 confusion with typhus. 



