348 BACTERIA IN INFECTIOUS DISEASES. 



the fever ; the uniform presence of which, during 

 the first invasion and the relapses, has been verified 

 by numerous observers in various parts of the 

 world. Inasmuch as the blood of healthy persons 

 is free from bacterial organisms of any kind, and 

 as this peculiar organism is not found in any other 

 febrile affection, the presumption is altogether in 

 favor of its causal relation. Looking at it from 

 another point of view, it is difficult to believe that 

 the vital fluid could be invaded by myriads of 

 active parasitic organisms, which must appropriate 

 to their own use material required to preserve the 

 integrity of the circulating fluid and for the nu- 

 trition of the tissues, without some disturbance 

 of the economy resulting. In other words, we can 

 easily understand that the presence of the spiro- 

 cha3te might give rise to the fever and other phe- 

 nomena of the disease ; but there is nothing in 

 our experience to indicate that fever causes the 

 appearance in the blood of parasitic organisms of 

 this description. 



The evidence in this case is very different from 

 that relating to the presence of micro-organisms 

 in morbid products of a low grade of vitality found 

 during life, or the demonstration post mortem of 

 similar organisms in the blood or tissues. And 

 while we may demand, as final proof, that the dis- 

 ease shall be produced by inoculation with a " pure 

 culture" of the parasite, yet, in the absence of 

 such demonstration, it must be admitted that the 

 evidence is very convincing as to the causal re- 



