442 RELAPSING FEVER 



by Soudake witch, who also produced the disease in two monkeys 

 (cercocebus fuliginosus) from which the spleen had been previously 

 removed, the animals having been allowed to recover completely 

 from the operation, and found that 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. Recent observations, however, in- 

 dicate that, as in the case of so many other diseases, the all- 

 important factor in the destruction of the organisms is the 

 development of antagonistic substances in the blood. Lamb 

 found in the case of the monkey (macacus radiatus) that the 

 removal of the spleen of an animal rendered immune by an 

 attack of the disease did not render it susceptible to fresh 

 inoculation, and attributed the immunity to the presence of 

 bactericidal bodies in the serum. He found, for example, that 

 in vitro the serum of an immune animal brought the movements 

 of the spirilla to an end, clumped them, and caused their dis- 

 integration ; and further, that when the spirilla and the immune 

 serum were injected in one case into a fresh monkey no disease 

 developed. In opposition to Soudake witch, Lamb found that 

 with a monkey from which the spleen had been removed death 

 did not occur after it was inoculated with the spirilla. Sawt- 

 schenko and Milkich found that there are developed during the 

 disease an immune body and an agglutinin, while Novy and 

 Knapp in their recent important work distinguish germicidal, 

 immunising, and agglutinating substances. They found that 

 the blood of the rat has no germicidal properties during the 

 onset of the disease, but that these appear and become well 

 marked during the decline. They produced a " hyper-immunity " 

 in rats by repeated injections of blood containing the spirilla, 

 and found that the serum of such animals had a markedly cura- 

 tive effect, and could cut short the disease in rats, mice, and 

 monkeys. 



In the case of the human subject it has been found that a 

 second attack of the disease can follow the first after a com- 

 paratively 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 short duration. The 

 course of events in the disease might be explained by supposing 

 that immunity of short duration is produced during the first 

 period of pyrexia, but that it does not last until all the spirilla 

 have been destroyed, some still surviving in internal organs 

 or in tissues where they escape the bactericidal action of the 

 serum. With the disappearance of the immunity the organ- 



