160 



AMETABOLA. 



of the body by a dark line, and inhabits the heads of children and 

 dirty persons, piercing the skin and sucking the blood. They are 



u. The common louse ; b, magnified ; c, one of the legs magnified ; d, eggs ; 

 e, ditto magnified. 



easily extracted by a fine tooth comb, or are destroyed by rubbing 

 calomel mixed with bears' grease into the roots of the hair. Its 

 eggs are small pear-shaped bodies, termed nits, which are 

 attached near the base of the hair by a glutinous substance. 

 Swammerdam and Leuwenhoeck, two of the most celebrated of 

 microscopic observers, have made the common louse the object of 

 very elaborate investigation. The former tells us, that notwith- 

 standing the great powers of propagation of this insect, " it is no 

 more than a jest that people say in sport that a louse may see 

 its fourth generation in the space of twenty-four hours ;" and 

 Leuwenhoeck, who put a male and female louse under a stocking 

 which he wore day and night to favour their breeding, found that 

 the female lays from fifty to a hundred eggs, and, computing the 

 natural increase from what he had seen, he says that in eight 

 weeks one louse may see five thousand of its descendants. It is 

 requisite that the eggs should be deposited in a place that is M'arm 

 and moderately moist to produce young, and hence many nits 

 laid on the hairs in the night-time are destroyed by the cold of 

 the succeeding day, and so stick for several months till they lose 

 their external form. In feeding, a constant motion of the intestines 

 may be perceived through the transparent skin, the blood rushing 

 like a torrent into the stomach. 



The term Phthiriasis has been given to a disease supposed to 

 originate entirely in attacks of the PediculL Kirby and Spence 

 have collected much information upon this subject, and conclude 

 their observations by doubting whether there be any real Phthiri- 



