RELAPSING FEVER 103 



strated in their blood. This paved the way for 

 further research, but no further discovery of 

 importance was made until the present decade 

 in regard to the European form of the disease. 



Meanwhile in Tropical Africa two workers, 

 Doctors Button and Todd, who had been sent 

 out by the Liverpool School of Tropical Medicine, 

 were studying the form of relapsing fever found 

 there, and which Todd thinks is identical with that 

 of the rest of the world. In Central Africa there 

 exists a tick called Ornithodorus moubata which 

 has habits similar to those of a bed-bug ; that is, 

 it lives in cracks in the walls and floors of the 

 native huts and issues forth at night to suck 

 blood. Full-grown it is about the size of a large 

 pea ; its skin is tough, grey, and wrinkled, and 

 it is able to survive many months without taking 

 food. Some of these ticks were fed on cases of 

 relapsing fever and afterwards on susceptible 

 animals, and these in time developed the disease. 

 It was also found that the offspring of such 

 infected ticks (to the third generation) could 

 similarly transmit the malady, the spirochaete 

 passing in some form from the parent to the egg 

 and so to the young. Judging from the analogy 

 of what was then known of the mode of trans- 

 mission of diseases by insects, the investigators 

 naturally thought that it was by means of the 

 bite itself that the virus was injected into the 

 blood. Some of the infected ticks were brought 

 to the Liverpool School, and a great deal of work 



