4 i 8 RELAPSING FEVER. 



thrown on these points by MetchnikorT, who produced 

 the disease in monkeys, and killed them at various stages 

 of the fever. He found that during the fever the spirilla 

 were practically never taken up by the leucocytes, but at 

 the time of the crisis the spirilla, on disappearing from the 

 blood, accumulated in the spleen and were ingested in 

 large numbers by the microphages or multi-nucleated leuco- 

 cytes. Within these they rapidly underwent degeneration 

 and disappeared. MetchnikofT also found that after the 

 spirilla had disappeared from the blood, the disease could 

 be produced in another animal by inoculations with spleen 

 pulp, in which the spirilla were contained within the leuco- 

 cytes, thus showing that they were living and active in the 

 spleen. It is to be noted in this connection that swell- 

 ing of the spleen is a very marked feature in relapsing 

 fever. These observations have been entirely confirmed by 

 Soudakewitch, who also showed that the destruction of the 

 spirilla in the spleen was an extremely rapid one, as they 

 were all destroyed ten hours after their disappearance from 

 the blood. He also produced the disease in two monkeys 

 from which the spleen had been previously removed, the 

 animals having been allowed to recover completely from 

 the operation. In these cases the spirilla did not disappear 

 from the blood at the usual time, but rather increased in 

 number, and a fatal result followed on the eighth and ninth 

 days respectively. Post mortem he found the spirilla in 

 enormous numbers throughout the blood vessels, and in 

 the portal vein they almost equalled the red blood -cor- 

 puscles in number. By these experiments it would appear 

 to be established that the spleen has an important function 

 in the destruction of the organisms. It has not been 

 shown, however, why the organisms disappear from the 

 blood at a particular time and accumulate in the spleen. 



In the case of the human subject it has been found 

 that a second attack of the disease can follow the first after 

 a comparatively short period of time, and it is often said 

 that one attack does not confer immunity. It is probably 

 rather the case that the immunity conferred is of very 



