440 RELAPSING FEVER 



though somewhat faintly, and are best coloured by the 

 Romanowsky method or one of its modifications. 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 considerable 

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

 found alive and active after many days. They are readily 

 killed at a temperature of 60 C., but may be exposed to 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 may occur after a similar interval. The spirilla begin to 

 appear in the blood shortly before the onset of the pyrexia, aud 

 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, and this experiment has been 

 several times repeated with the same result. Additional proof, 

 that the organism is the cause of the disease has been afforded by 

 experiments on animals. Carter in 1879 was the first to show that 

 the disease could be readily produced in monkeys, and his experi- 

 ments were confirmed by Koch. In such experiments the blood 

 taken from patients and containing the spirilla was injected sub- 

 cutaneously. In the disease thus produced there is an incubation 

 period which usually lasts about three days. At the end of that 

 time the spirilla rapidly appear in the blood, and shortly after- 

 wards the temperature quickly rises. The period of pyrexia 

 usually lasts for two or three days, and is followed by a marked 

 crisis. As a rule there is no relapse, but occasionally one of 

 short duration occurs. 1 White mice and rats are also susceptible 



1 Norris, Pappenheimer, and Flournoy, in their experiments on monkeys 

 in America, found that several relapses occurred. 



