416 RELAPSING FEVER. 



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 2 to 6 times the diameter of a 

 red blood corpuscle. 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. 101). 

 They are actively motile, and may be seen moving quickly 

 across the microscopic field with a peculiar movement 

 which is partly twisting and partly undulatory, and dis- 

 turbing the blood corpuscles in their course. 



They stain with watery solutions of the basic aniline 

 dyes, though somewhat faintly, and are best coloured in 

 film preparations by LofHer's or Kiihne's methylene-blue 

 solutions. When thus stained they usually have a uniform 

 appearance 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 con- 

 siderable 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 tempera- 

 ture which lasts for about five to seven days. At the end 

 of this time a crisis occurs, the temperature falling rapidly 

 to normal. In the course of about seven days another 

 sharp rise of temperature takes place, but on this occasion 

 the fever lasts a shorter time, again suddenly disappearing. 

 A second or even third relapse may occur. The spirilla 

 begin to appear in the blood shortly before the onset of 

 the pyrexia, and during the rise of temperature rapidly 

 increase in number. They are very numerous during the 



