510 KELAPSING FEVER 



produced in monkeys, and his experiments were confirmed by 

 Koch. In such experiments the blood taken from patients and 

 containing the spirochsetes was injected subcutaneously. In the 

 disease thus produced there is an incubation period which usually 

 lasts about three days. At the end of that time the organisms 

 rapidly appear in the blood, and shortly afterwards the tempera- 

 ture quickly rises. The period of pyrexia usually lasts for two 

 or three days, and is followed by a marked crisis. As a rule 



Bt 



t ^ 



k jflK^^^R^kk 



FIG. 153. Spirochaete Obermeieri in blood of infected mouse, 

 x 1000. 



there is no relapse, but occasionally one of short duration occurs. 1 

 White mice and rats are also susceptible to infection. In the 

 former animals the disease is characterised by several relapses, 

 in the latter there is, however, no relapse. 



Immunity. Metchnikoff found that during the fever the 

 spirochsetes were practically never taken up by the leucocytes in 

 the circulating blood, but that at the time of the crisis, on dis- 

 appearing from the blood, they accumulated in the spleen and 



1 Norris, Pappenheimer, and Flournoy, in their experiments on monkeys 

 with the organism of American relapsing fever, found that several relapses 

 occurred. 



