88 LICE AND THEIR MENACE TO MAN 



approximate times at which the secondary hosts 

 were first bitten. The migrations of the lice are 

 also shown in a graphical manner in Charts I. 

 and II. In each of these the successive points 

 on the curves represent the percentages of the 

 numbers of lice in the following positions : (1) 

 inside the pyjamas of the primary host, including 

 the ones on the body ; (2) outside the pyjamas 

 of the primary host and on the contiguous 

 blanket surfaces, i.e. those which had left him 

 but had not wandered f ar ; (3) outside the 

 pyjamas of the secondary host and on the con- 

 tiguous blanket surfaces, i.e. those which had 

 definitely migrated and which would have pre- 

 sumably passed on to the secondary host for their 

 next feed ; (4) inside the pyjamas of the secondary 

 host, i.e. those which had migrated and already 

 established themselves on him ; (5) those which 

 had wandered far, and for the time being lost 

 themselves between the upper blankets and 

 which might have passed back to either host 

 had the experiment been more protracted ; (6) 

 those which were not recovered and which were 

 either overlooked in the search or had left the 

 bed. This last number was fairly constant. 

 The number which had wandered far on the 

 blankets was also fairly constant and very small, 

 except in Experiment 3, owing to the restless- 

 ness of the men disarranging the bed, and in 

 Experiment 4, owing to the blankets overlapping 

 and not completely covering one another. It 



