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CHAPTER XIY. 
THEIR NATURAL WEAPONS. 
Having treated of the courage, ferocity, and cunning of 
4:ats, we shall now proceed to notice those formidable weapons 
with which nature has endowed them, viz., their teeth. 
The propensity of these animals for gnawing is not merely 
the result of a reckless determination to overcome impedi- 
ments, but a necessity of their existence. " The rat" (says 
Bentley's Miscellany") " has four formidable weapons in the 
shape of long sharp teeth ] two in front of the upper-jaw, 
and two corresponding in the lower. These are formed in the 
shape of wedges ; and, by the following wonderful provision 
of nature, have always a fine, sharp, cutting edge. On 
examining them carefully, we find that the inner part is of a 
soft ivory -like composition, which may be easily worn away; 
whereas the outside is composed of glass-like enamel, which 
is excessively hard. The upper- teeth wwk exactly into the 
under, so that the centres of the opposed teeth meet exactly 
in the act of gnawing j the soft part is thus being perpetually 
worn away, while the hard part keeps a sharp chisel-like 
edge ; at the same time, the teeth keep growing up from the 
bottom, so that, as they wear away, a fresh supply is ready. 
Thus the ceaseless working of the rat's incisor- teeth against 
some hard substance is absolutely necessary* to keep them 
down ; and if he did not gnaw for his subsistence, he would 
be compelled to gnaw, to prevent his jaw being gradually 
locked by the rapid development." 
In consequence of the arrangement of nature just de- 
scribed, there is a belief current, that if one of the teeth 
be removed, either by force or accident,^ the corresponding 
tooth will continue to grow, and, as there is nothing to grind 
it away, will increase till it turns upon itself, and forms a 
perfect ring. They also state, that if it be an under-tooth 
it sometimes will even run into the skull above. " Bentley's 
Miscellany " states, that there is a preparation in the 
Museum of the Boyal College of Surgeons which illustrates 
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