PESTS OF THE HOUSEHOLD. 67 



nimble little feet across the floor. Indeed, we may say 

 that houses are built for men and mice : they go in to- 

 gether, they live together ; and not until the last human 

 occupant departs do the gnawings and squeakings cease. 



2. The rat and the mouse are rodents, animals made 

 for gnawing, and gnaw they must. The nose of a rat is 

 pointed, and in the front part of each jaw are two chisel- 

 like teeth. On examining them we find that the inner 

 part is of an ivory-like substance, which is easily worn 

 away, while the outside is composed of a glass-like 

 enamel, which is excessively hard. The upper teeth 

 work exactly into the under, in the act of gnawing, so 

 that the soft part is continually worn aw^ay, while the hard 

 part keeps a sharp, chisel-like edge. At the same time 

 the teeth grow up from the bottom, so that as they wear 

 away they are continually renewed. 



3. In consequence of this arrangement, if one of the 

 teeth be removed or accidentally broken, the opposite tooth 

 will continue to grow, until it will project from the mouth 

 and cease to be of any use. Rats have been killed with 

 an upper tooth grown long and bent into a complete 

 circle, or with an under tooth piercing the skull above. 

 The ceaseless gnawings are thus seen to be a necessity, 

 for, if the rat did not gnaw for a living, he would be 

 obliged to gnaw to prevent his teeth from growing so as 

 to fill his mouth and render his jaws useless. 



4. These pests of the household live in the hollow 

 spaces in the walls, in burrows opening from the cellar- 

 bottoms, in drains, and in all sorts of out-of-the-way holes 

 and crevices. Wherever there is a place for a rat there 

 is a rat to occupy it. Both rats and mice increase with 

 such fearful rapidity that if they were not kept down 

 they would soon overrun a house and render it unin- 

 habitable by human beings. It is estimated that a pair of 



