MIGRATION OF BODY-LICE 97 



Summary. The lice were placed on the 

 primary host at the beginning of the experiment, 

 being emptied into a heap on his skin, and had 

 not settled down there as in the case of a man 

 in a normal lousy condition. The results must 

 not be taken to mean that under natural condi- 

 tions the migration of lice from a man in bed 

 would necessarily be as high as the experiments 

 indicate. That some migration would occur 

 under natural conditions in bed is, however, 

 certain, since there is no obvious reason why 

 these should have been averse to the quarters 

 allotted them on the normal men. Incidentally 

 also, the experiments emphasise the importance 

 of treating the blankets of lousy men in any 

 scheme of disinfestation. 



There was a very marked difference in the 

 behaviour of the lice in the two series of experi- 

 ments. This difference was marked by the in- 

 creased migration from the primary host when 

 he was febrile. This will be seen by reference to 

 Chart III. In this chart the points on the 

 curves represent the migrations of the lice to 

 the same points as in Charts I. and II. The 

 continuous line represents the wanderings of the 

 600 lice used in Experiments 1 to 3, while the 

 broken line represents the wanderings of those 

 in Experiments 4 to 6. From this it will be seen 

 that when both men were afebrile, 62 per cent of 

 the lice remained on or near the primary host, 

 35*5 per cent being inside his pyjamas, while 



H 



