SPIROCHJETES IN LICE 83 



North African relapsing fevers, has not been fully 

 worked out. The mode of transmission is very 

 different from that of 5. duttoni, and it is possible 

 that there will be some differences in the life-cycle 

 when that is completely known. The long labour 

 of Nicolle, Blaizot, and Conseil on the mode of 

 transmission of 5. recurrentis and its North African 

 varieties has resulted in establishing the body louse 

 as the means whereby the fever is spread. Watch- 

 ing the sequence of events in Nature, it was found 

 that the victims of spirochaetosis were often not so 

 situated as to be attacked by bugs or ticks, but that 

 many of them harboured lice on their persons or in 

 their clothing. Lice, then, seemed the likely trans- 

 mitters, and it was assumed at first that the disease 

 was spread by their bites. 



One of the above workers then fed lice known to 

 be infected with spirochsetes on himself, using over 

 five thousand in one experiment. No infection fol- 

 lowed, though many thousands of bites were 

 received. The experiment was repeated, but still 

 no infection ensued. The spirochsetes, then, were 

 not inoculated by the bite of the louse, and another 

 method was sought. Again, what happened in 

 Nature ? The irritation of the louse-bite caused the 

 victim to scratch, and by so doing, one or more lice 

 were crushed on to the skin. This, then, seemed a 

 channel of infection. One of the above workers 

 scratched his own skin, and put the contents of two 

 lice known to contain spirochaetes on the slight 

 abrasion thus produced. Infection followed in about 

 five days. The experiment was repeated both on 



