RELATIONS OF SPIRILLUM TO DISEASE. 417 



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, and 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 experi- 

 ment has been several times repeated with the same result ; 

 after a period of incubation the spirilla begin to appear in 

 the circulating blood, and their appearance is soon followed 

 by the occurrence of pyrexia. 



Numerous attempts to cultivate this organism outside 

 the body have all been attended with failure, and it has 

 been abundantly shown that it does not grow on any of 

 the media ordinarily in use. Koch found that on blood 

 serum the filaments of the spirilla increased somewhat in 

 length, and formed a sort of felted mass, but that no multi- 

 plication took place. Additional proof, however, that the 

 organism is the cause of the disease has been afforded by 

 experiments on monkeys, and facts of considerable interest 

 have been thus established. Carter in 1879 was tne fi rst 

 to show that the disease could be readily produced in 

 these animals, and his experiments were confirmed by 

 Koch. In such experiments the blood taken from patients 

 and containing the spirilla was injected subcutaneously. 

 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 

 afterwards the temperature quickly rises. The period of 

 pyrexia usually lasts from two to three days, and is followed 

 by a marked crisis. As a rule there is no relapse, but 

 occasionally one of short duration occurs. The presence 

 of spirilla in the blood has the same relation to the pyrexial 

 period as in the human subject. 



For a long time the place and mode of destruction of 

 the spirilla were quite unknown, but valuable light was 

 27 



