AFRICAN TICK FEVER 513 



German East Africa, on the other, that our knowledge of the 

 etiology of the disease has been obtained. 



The following are the chief facts regarding this fever. 

 Clinically, the fever closely resembles relapsing fever, but the 

 periods of fever are somewhat shorter, rarely lasting for more 

 than two or three days. It is seldom attended with a fatal result 

 unless in patients debilitated by other causes. The organisms in 

 the blood are considerably fewer than in the case|of European 



*.,■■/ 



Fig. 155. — Spirillum of human tick fever (spirillum duttoni) in 

 blood of infected mouse, x 1000. 



relapsing fever, and sometimes a careful search may be necessary 

 before they are found. Morphologically, they are said to be 

 practically identical, although Koch thought that the organisms 

 in tick fever tended on the whole to be slightly longer ; the 

 average length may be said to be 15-35 p. Dutton and Todd 

 showed that it was possible to transmit the disease to certain 

 monkeys (cercopitheci) by means of ticks which had been allowed 

 to bite patients suffering from the disease, the symptoms in 

 these animals appearing about five days after inoculation. The 

 disease thus produced is characterised by several relapses, and 



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