TRENCH FEVER 127 



these two men by allowing lice taken from trench 

 fever patients to feed on them. Nothing hap- 

 pened though the experiments were continued 

 for many weeks, but as we anxiously watched 

 the men from day to day we were struck by the 

 fact that they never scratched their skin where 

 the lice had bitten. Now the average soldier 

 suffers considerably from the irritation of the 

 lice upon him and scratches himself accordingly. 

 It occurred to us, therefore, that herein might lie 

 the explanation of what, at first, seemed a dis- 

 appointing failure. Cole and Edgeler were old 

 and tough ; the man of military age had a skin 

 that was far more irritable. The latter scratched 

 himself ; our volunteers did not. Was scratching 

 an essential to infection ? To test this possibility 

 the skin of a new volunteer named D. Sullivan 

 was on 5th February 1918 scratched by means of 

 a needle, and the droppings of the lice feeding on 

 Cole and Edgeler rubbed into it. A week later 

 Sullivan developed trench fever, and as a result 

 the usual method of transmission of the disease 

 had been demonstrated, for we have repeated this 

 and similar experiments many times since with 

 unfailing success. Further work, however, has 

 shown that men bitten by infected lice, but who 

 do not scratch themselves, may in some instances 

 contract trench fever. Such happenings are the 

 exception and not the rule, and are probably the 

 result of lice depositing their droppings on the 

 openings made in the skin by their own bites. 



