RELAPSING FEVER 207 



probably of the genus Culex. The spirochseta circulates 

 in the blood during attacks and settles in the spleen 

 between them. The disease is characterized by inter- 

 mittent attacks of continued fever beginning suddenly, 

 lasting four to six days, and ending by crisis. The 

 febrile periods recur with eight to ten day intervals of 

 freedom from symptoms. Blood is examined during the 

 fever and we find under the microscope long, ^QQ~Q 

 inch, delicate, ^Q^-Q-Q inch wide, wavy spirals with 



FIG. 60 



Spirochaeta Obermeieri blood smear. Fuchsin. X 1000 diameters. (From 

 Itzerott and Niemann.) 



corkscrew and undulatory movements. They have 

 not been successfully cultivated, but it is known that 

 they are not very resistant to deleterious agencies. 

 Some immunity is left after an attack, and use has 

 been made of the serum in treating the sick. There 

 are several species of this spirochete, differing very 

 slightly, and to make an antiserum it is necessary to 

 use many varieties. Texas and African tick fever are 

 due to this genus 



