GENERAL CHARACTERS OF SPIROCILETES. 45 



PATHOGENICITY. 



Since it has been found impossible to produce pure 

 cultures of any spirochsetes, rigorous proof of their 

 causal connection with disease, such as is demanded 

 by the well-known "postulates" of Koch, cannot be 

 furnished. Nevertheless, the pathogenicity of certain 

 forms appears to be fairly established. 



RELAPSING FEVER. 



In the case of relapsing fever the spirochaete dis- 

 covered by Obermeier and generally known by his name 

 is universally admitted to be the exciting cause of the 

 disease. It is present in all cases of the malady; it 

 disappears during the remissions and reappears during 

 the relapses. The blood of a patient reproduces a similar 

 affection when injected into animals, and no other germ 

 has been found present which might be looked upon as 

 pathogenic. 



The disease is characterised by a sudden onset, after 

 an incubation-period of varying length (from a few 

 hours up to fourteen days). The first access of fever 

 lasts about a week and ends by crisis. A period of 

 apyrexia ensues, to be followed by a second access of 

 fever, and this sequence may be repeated a third and 

 even more times. The spleen and liver are much en- 

 larged, and the spirochaete may be found in the spleen 

 during the remissions. Monkeys are the only lower 

 animals directly susceptible to the disease. 



In mankind infection may be conveyed by direct 

 inoculation, as by a scratch at a necropsy; it may 

 also occur by aerial conveyance in some instances, like 

 the infection in scarlet fever, typhus, etc. 1 It has 

 been supposed that the infection may be conveyed 



1 Ker, "Infectious Diseases" London, 1908, p 229. 



