INTRODUCTORY 7 



Others are so irritated by the itching that they 

 will scratch away large surfaces of skin, leaving 

 bleeding wounds. Generally speaking, the bite 

 is less irritating than that of the flea or the bed- 

 bug, but to a few people, to whom the bites of 

 these are a matter of no account, louse-bites are 

 a source of real annoyance. This varying re- 

 action of different people to bites is general with 

 all blood -sucking insects. The first effect of a 

 bite is a small red mark, usually not raised, about 

 an eighth of an inch across. This usually dis- 

 appears and cannot be seen after an hour or so. 

 Later it may reappear and begin to itch, or it may 

 not be seen again. The actual bite sometimes 

 causes a slight pricking sensation if the wound 

 is near a nerve-ending. If a number of lice bite 

 near together the flushing of the skin may be 

 fairly extensive. Occasionally at the position of 

 each bite a small watery blister appears the 

 following day. After a day or two this collapses, 

 leaving a brown bronze scab, which persists for 

 days before it finally peels off. Bronzing of the 

 skin may follow the bites without any previous 

 blistering. By repeated and extensive biting 

 large areas of skin may be discoloured in this 

 way, becoming very dark and retaining the 

 colour for a long time. The condition into which 

 a person may be brought by this is shown in the 

 photograph (Fig. 2), which represents the back 

 of a soldier evacuated from France with trench 

 fever. The whole surface of the trunk was 



