448 RELAPSING FEVER. 



disease was produced in the human subject by inoculations with 

 blood containing the organisms, and a similar condition has been 

 produced in apes. 



Characters of the Spirillum. The organisms as seen in the 

 blood during the fever are delicate spiral filaments which have a 

 length of from two to six times the diameter of a red blood cor- 

 puscle. They are, however, exceedingly thin, their thickness 

 being much less than that of the cholera spirillum. They show 

 several regular sharp curves or windings, of number varying 

 according to the length of the spirilla, and their extremities are 

 finely pointed (Fig. 153). They are actively motile, and may 



be seen moving quickly across 

 the microscopic field with a pe- 

 culiar movement which is partly 



v r *~ ^JalnMili* S* 



twisting and partly undulatory, 

 and disturbing the blood cor- 

 y%ftgP^J\ puscles in their course, 

 jgftk They stain with watery 



solutions of the basic aniline 



^^^^^B! -i?^b 



dyes, though somewhat faintly, 

 anc ^ are b est coloured in film 

 preparations of Lofrler's or 

 Kiihne's methylene-blue solu- 

 FIG. i 53 .-s P iriiia of relapsing fever in tions. When thus stained they 

 human blood. Film preparation. usually have a uniform appear- 



(After Koch.) x about 1000. 



ance throughout, or may be 



slightly granular at places, but they show no division into short 

 segments. They lose the stain in Gram's method. 



In blood outside the body the organisms have a considerable 

 degree of vitality, and when kept in sealed tubes have been 

 found alive and active after many days. They are readily killed 

 at a temperature of 60 C, but may be exposed to o C. without 

 being killed. There is no evidence that they form spores. 



Relations to the Disease. In relapsing fever, after a period 

 of incubation, there occurs a rapid rise of temperature which lasts 

 for about five to seven days. At the end of this time a crisis 

 occurs, the temperature falling quickly to normal. In the course 

 of about other seven days a sharp rise of temperature again 

 takes place, but on this occasion the fever lasts a shorter time, 

 again suddenly disappearing. A second or even third relapse 



