264 NATURAL THEOLOGY. 



with its articulation ; but the instances already 

 given of adaptation may suffice. 



Before leaving the subject of the provisions 

 against the wasting of the teeth by friction, there 

 are one or two circumstances of a very interesting 

 nature to be noticed. The elephant is a graminiv- 

 orous animal, and requires to grind its food very 

 thoroughly. What then must be the provision in 

 the grinding tooth of this animal to withstand the 

 power of its jaws ? We find the teeth, in fact, 

 formed of three substances, and, we may say, of a 

 structure superior to the teeth of the lesser grami- 

 nivorous animals, of course admirably suited to 

 resist the action of chewing. But there is a cir- 

 cumstance peculiar here. Although the matter of 

 the tooth once formed does not change, an altera- 

 tion in the position of the tooth in the jaw may 

 produce a similar result. When the great grind- 

 ing tooth of the elephant appears first above the 

 jaw, the anterior corner only projects ; but as that 

 becomes worn down, the tooth by revolving on its 

 centre, presents in slow, but regular succession, 

 more and more of the surface, guarded with new 

 plates of enamel, until it is at last worn to the 

 roots. Here, the^, we have a new and extraor- 

 dinary provision against attrition in the teeth of an 

 animal which lives to a great age. The structure 

 of the tooth itself has a very large proportion of 

 enamel, in dense and regular ridges : but as if the 

 material of the teeth could be brought to no greater 

 perfection to withstand the chewing, it is " con- 



