672 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



the disease; the infection may be transmitted, from mother to daughter, through at least 

 three generations of ticks. 



The ticks hide during the day and feed at night. The wound produced by their 

 bite is insignificant. 



An incubation period of about five days intervenes between the tick 

 bite and the appearance of symptoms. The fever is characteristic; it 

 rises rapidly to, perhaps, 105 and it remains high for from three to five 

 days. It then falls suddenly and there is no fever for from five days 

 to two weeks. Then the temperature rises again. There may be from 

 three to six such recurrences of fever before the illness ends. The 

 definite periodicity of the relapses probably depends upon some more 

 or less regular developmental change in the spirochaetes; they are always 

 most numerous in the blood during the height of the fever. The disease 

 is not often fatal. There is no specific treatment for it. It can be 

 prevented easily by avoiding tick bites. 



RELAPSING OR RECURRENT FEVER. 



Spirochata obermeieri. 



This is still a common disease in some parts of Europe. Its symp- 

 toms are almost identical with those of tick fever; and the spirochaete 

 causing it, Spirochata obermeieri, can only be distinguished from 

 Spirochata duttoni by the fact that an animal which has recovered from 

 an infection by one of these parasites is immune to reinoculation with it, 

 but is susceptible to an inoculation with the other spirochaete. The means 

 by which relapsing fever is transmitted is not known; it is probably 

 carried by the bites of lice, or of other vermin. 



YAWS. 

 Spirochceta pallidula. 



This is a disease of the tropics. It is characterized by the presence, 

 on any part of the body, of more or less numerous, ulcerating sores. 

 It is caused by a slender spirochaete, Spirochceta pallidula. 



OTHER SPIROCELETAL DISEASES. 



ULCERATING GRANULOMA OF THE PUDENDA is a tropical disease which 

 is also caused by a spirochaete. 



Spirochaetes cause diseases of geese in Southern Russia and of fowls 



