450 RELAPSING FEVER. 



keys 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 in the circulating blood, but that at the time of 

 the crisis on disappearing from the blood, they accumulated in 

 the spleen and were ingested in large numbers by the microphages 

 or polymorpho-nuclear leucocytes. Within these they rapidly 

 underwent degeneration, and disappeared. Metchnikoff 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 

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

 spleen. It is to be noted in this connection that swelling 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 of a 

 monkey (Cercocebus fuliginosus) 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 hav- 

 ing 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 

 corpuscles in number. These experiments would appear to es- 

 tablish the important function of the spleen in the destruction of 

 the organisms ; they do not show, however, why the organisms 

 disappear from the blood at a particular time and accumulate in 

 the spleen. 



Views of a different character have been advanced by Lamb. 

 According to this observer, while in the monkey (Macacus radia- 

 tus) a relapse rarely occurs, this animal about a month after 

 recovery is susceptible to fresh inoculation. During the two or 

 three weeks following an attack of the fever it, however, mani- 

 fests a degree of immunity to infection. If in such an animal 

 the spleen be excised, it still does not suffer from the disease 

 after fresh inoculation. The immunity Lamb attributes to the 

 presence of bactericidal bodies in the serum. The proof of this 

 advanced is that in vitro the serum brings the movements of the 



