104 LICE AND THEIR MENACE TO MAN 



was done with this strain of the parasite. 

 Attempts were made to transmit it by the bites 

 of other vermin, fleas, lice, and bed-bugs. None 

 of these were successful, with the exception of one 

 experiment of Nuttall's, in which a bed-bug was 

 allowed to partly feed on an infected animal and 

 then to complete its meal on another animal 

 while its proboscis was still wet with the blood 

 of the first. The second animal developed the 

 disease, but this did not suggest that this was a 

 normal mode of conveyance of the disease in 

 nature. It was therefore concluded that the 

 bites of these vermin did not transmit relapsing 

 fever. Todd now thinks that it is not the actual 

 bite of the tick either which causes it. While the 

 tick is feeding, an operation which occupies two 

 or three hours, a quantity of fluid flows from two 

 glands on the lower side of the body and forms a 

 film between it and the skin. At the same time 

 it discharges from the anus a small quantity of a 

 whitish excrement which mixes with the fluid. 

 Both the fluid and the excrement contain small 

 spirochaetes, and these probably penetrate the 

 wound caused by the bite, thus causing the 

 disease. 



Though the bites of lice did not cause relapsing 

 fever it was still thought that the vermin had 

 some connection with the disease, and this was 

 finally proved to be the case by Dr. Sergent, 

 working in Algeria, where it is almost constantly 

 epidemic. He showed that if body-lice were fed 



