178 THE PROTOZOA. 



formerly considered a bacterium and was termed the Spirochaeta 

 obermeieri. It is present in the blood of persons suffering from the 

 disease during the pyrexia. During the apyrexia they are not found in 

 the peripheral circulation. At this time they are present in great 

 numbers in the spleen where they are actively phagocytized. The 

 disease is supposed to be transmitted by bed-bugs or lice. Monkeys 

 are susceptible and, after passage through monkeys, rats can be 

 inoculated. 



S. duttoni. This is the cause of South African tick fever or Tete 

 fever. The disease is similar to relapsing fever, but there are generally 

 four or five febrile paroxysms with apyrexial intervals. The disease is 

 readily transmitted to ordinary laboratory animals, especially the rat. 

 Rats which have recovered from S. recurrentis can be infected by 

 S. duttoni and vice versa. The disease is transmitted by the bite 

 either of the adult or larval Ornithodoros moubata. Koch found 

 spirochaetes in the eggs of the ovaries of ticks which had fed on persons 

 with the disease. It is thus an instance of hereditary transmission. 



Other spirochaetes that have been considered as pathogenic for the 

 type of relapsing fever in India and that of America are the S. carteri 

 and the S. novyi. 



S. vincenti. This is a very delicate spiral-shaped organism 

 which has been found in conjunction with a fusiform bacillus in a 

 throat inflammation, usually termed Vincent's angina. 



S. refringens. This Spirochaeta is frequently associated with the 

 Treponema pallidum and is common in genital ulcerations. It is 

 thicker, has less regular and more flattened curves and stains more 

 readily. 



Treponema. 



The genus Treponema has no undulating membrane and has a 

 flagellum at each end. 



Treponema pallidum. This is the cause of syphilis. It is char- 

 acterized by its very geometric regularity in the spirals, which are 

 deeply cut, and in focussing up and down continue in focus (like a 

 corkscrew). They require from one to two hours to stain distinctly 

 with Giemsa's stain and the attenuated ends or flagella should always 



