14 ANIMAL PAEASITES 



The animal holds on so tight, that it will be 

 crushed before it relaxes the grasp of the hair ; 

 it deposits its eggs, the nits, on the hair, just as 

 the pediculus capitis does ; but as it cannot run 

 about, these are always placed on the hair close to 

 the skin, and hence often overlooTced. To this wo 

 shall recur again, when speaking of the treatment of 

 these vermin. This animal lives on all the haired 

 portions of the body except the scalp, which is the 

 domain of the pediculus capitis. They never in- 

 terfere with each other. When both are present 

 on the same person, the head-louse will be found 

 on the hair of the head, down, for instance, to the 

 whisker, and never below ; whilst the crab-louse 

 infests the whiskers up to the scalp, which he never 

 occupies ; he does, however, take possession of 

 the eyebrows and eyelashes. Why this is, is not 

 yet known. The insect is transferred from one 

 individual to another by contact, and by the agency. 

 of clothes, linen, and beds. It is said to be most 

 abundant in southern climates. 



This pediculus lives on human blood, and, in 

 obtaining it from the skin by biting deeply and 

 firmly, it causes often considerable irritation, 

 varying, of course, with the cutaneous sensibility 



