274 NATURAL THEOLOGY. 



hanging from above, intervene between the plates 

 of bone, and there perform their peculiar secre- 

 tion, depositing the enamel. But it would appear 

 that these processes, becoming at length tightly 

 embraced by the plates of enamel which they 

 have themselves secreted, throw out a less perfect 

 material, as it w^ere ; this is called the crusta 

 petrosa or cement. When the tooth thus formed 

 rises above the gum, and when attrition wears 

 down a part of it, the interstices caused by the 

 wasted processes of the septa of the sac are ex- 

 posed, and the food is crammed down into these 

 crevices, and then on making a section of the tooth 

 we may discover four substances, ivory, enamel, 

 crusta petrosa, and foreign matter, in alternate 

 layers. 



Now, contemplating the slow formation of the 

 teeth whilst yet deep in the jaw, — their curious 

 mode of growth, adapted to the form of the jaw, 

 — the articulation of the jaw with the head, — 

 the position and powers of the muscles that are 

 to move the jaw, with the means to be employed 

 by the animal in gathering, masticating, and di- 

 gesting its food, — we can desire no more absolute 

 proof of prospective contrivance and design. 

 Were we to seek further, we have only to com- 

 pare these mechanical appliances with the in- 

 stincts and propensities of the animals. 



There is but one thing more worthy of atten- 

 tion in the teeth, than their mechanism, we mean 

 their vital properties. Is it not a wonderful thing 



