RELATIONS OF SPIRILLUM TO DISEASE. 445 



are finely pointed (Fig. 115). 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 disturbing 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 Loffler'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 quickly 

 to normal. In the course of about another seven days a 

 sharp rise of temperature again takes place, but on this occa- 

 sion the fever lasts a shorter time, again suddenly disappear- 

 ing. A second or even third relapse may occur after a similar 

 interval. 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 fever, a large number being often 

 present in every field of the microscope when the blood is 

 examined at this stage. They begin to disappear shortly 

 before the crisis : after the crisis they are entirely absent 

 from the circulating blood. A similar relation between the 

 presence of the spirilla in the blood and the fever is found 

 in the case of the relapses, whilst between these they are 

 entirely absent. Munch in 1876 produced the disease in 

 the human subject by injecting blood containing the spirilla, 



