164 THE MORE CHRONIC INFECTIOUS DISEASES 



for the African variety, which spreads by means of a 

 tick. The spirochete circulates in the blood during 

 attacks and settles in the spleen between them. The 

 disease is characterized by intermittent attacks of 

 continued fever beginning suddenly, lasting four to 

 six days, and ending by crisis. The febrile periods 

 recur with eight to ten days intervals of freedom 

 from symptoms. Blood is examined during the fever 

 and we find under the microscope long, ^irW inch, 



FIG. 44. Spirochaeta Obermeieri blood smear. Fuchsia. X 1000 

 diameters. (Fi;om Itzerott and Neimann.) 



delicate, Troirdo" mcn w ^e, wavy spirals with corkscrew 

 and undulatory movements. 



The spirochetes have been cultivated, under anaerobic 

 conditions, in serum supplied with fresh animal tissue 

 and these cultures may be transferred to monkeys 

 and mice. Some immunity is left after an attack, 

 and use has been made of the serum in treating the 

 sick. As there are several species of this spirochete, 

 differing very slightly, and to make an antiserum it is 

 necessary to use many varieties. 



