SPECIFICITY IN TRANSMISSION. 87 



malaria, only Glossina flies appear to transmit na- 

 gana and sleeping sickness, and only Dermacentor 

 ticks carry Eocky Mountain spotted fever. An 

 exception is found to this in the case of a spiril- 

 losis of fowls in South America. Naturally this 

 disease is transmitted by a species of tick, Argas 

 miniatus, but experimentally ib may also be trans- 

 mitted by OrnitJiodorus moubata. The latter, in 

 addition to transmitting the disease just men- 

 tioned, may also carry the European relapsing 

 fever, and is habitually concerned in the convey- 

 ance of the South African tick fever of man. 



