DIRECT INJURIES CAUSED BY INSECTS. 83 



I hope I shall not too much oiFend your delicacy if I 

 begin the first class of our insect assailants with a very 

 disffustinff senus, which Providence seems to have created 

 to punish inattention to personal cleanliness. But though 

 this pest of man must not be wholly passed over, yet, 

 since it is unfortunately too well known, it will not be at 

 all necessary for me to enlarge upon its history. I shall 

 only mention one fact which shows the astonishingly rapid 

 increase of these animals, where they have once gotten 

 possession. It is a vulgar notion, that a louse in twenty- 

 four hours may see two generations ; but this is rather 

 overshooting the mark. Leeuwenhoek, whose love for 

 science overcame the nausea that such creatures are apt 

 to excite, proves that their nits or eggs are not hatched 

 till the eighth day after they are laid, and that they do 

 not themselves commence laying before they are a month 

 old. He ascertained, however, that a single female louse 

 may, in eight weeks, witness the birth of five thousand 

 descendants *. You remember how wolves were extir- 

 pated from this country, but perhaps never suspected any 

 monarch of imposing a tribute of lice upon his subjects. 

 Yet we are gravely told that in Mexico and Peru such a 

 ^oZZ-tax was exacted, and that bags full of these treasures 

 were found in the palace of Montezuma'' ! ! ! Were our 

 own taxes paid in such coin, what little grumbling would 

 there be ! 



Two other species of this genus, besides the common 

 louse, are, in this country, parasites upon the human 

 body But already I seem to hear you exclaim, "Why 



' Leeuw. E'pid. 98. 1696. 



" Bingley, Anim. Biogr. first edition, iii. 437. St. Pierre's Studies, 

 Sec. i. 312' 



g2 



