DISEASES CAUSED BY SPIROCHETES 



609 



even four attacks may occur, but the disease is not very often fatal. 

 Wlien patients do succumb, however, the autopsy findings are not 

 particularly characteristic. Apart from the marked enlargement of 

 the spleen, which histologically shows the changes indicating simple 

 hyperplasia, and a shght enlargement of the liver, no lesions are found. 

 The diagnosis is easily made during the febrile stage by examination of 

 a small quantity of blood under a cover-shp or in the hanging-drop 

 preparation. 



Several types of relapsing fever have been described. In Africa the 

 disease has long been prevalent in many regions and the investigations 

 of Ross and Milne,' Koch,^ Button and Todd,^ and others have brought 



Pig. 135. — Spirochete of Dtttton, African Tick Fever. (From prepara- 

 tion furnished by Dr. G. N. Calkins.) 



to light that many conditions occurring among the natives, formerly 

 regarded as malarial, are caused by a species of spirochsete. Whether 

 or not the microorganisms observed in the African disease are exactly 

 identical with the spirochsete observed by Obermeier is yet a question 

 about which several opinions are held. Button and Todd beheve that 

 the same microorganism is responsible for both diseases. Koch, on the 

 other hand, beUeves that the slightly smaller size of the African spiro- 

 chsete and the milder course of the clinical symptoms indicate a defi- 

 nite difference between the two. Animal experiments made with the 

 African organism, furthermore, usually show a much more severe in- 

 fection than do similar inoculations with the European variety. The 



' Ross and Milne, Brit. Med. Jour., 1904. 

 ^ Koch, Deut. med. Woch., xxxi, 1905. 



' Dutlon and Todd, Lancet, 1905, and Jour, of Trop. Med., 1905. 

 40 



