100 THEORY OF THE EARTH. 



fitted by nature ; and, from each of these particular 

 modifications, there result certain differences in 

 the more minute conformations of particular parts, 

 all, however, conformable to the general prin- 

 ciples of structure already mentioned. Hence it 

 follows, that in every one of their parts we dis- 

 cover distinct indications, not only of the classes 

 and orders of animals, but also of their genera, 

 and even of their species. 



In fact, in order that the jaw may be well adapt- 

 ed for laying hold of objects, it is necessary that 

 its condyle should have a certain form ; that the 

 resistance, the moving power, and the fulcrum, 

 should have a certain relative position with res- 

 pect to each other ; and that the temporal mus- 

 cles should be of a certain size ; The hollow or 

 depression, too, in which these muscles are lodged, 

 must have a certain depth ; and the zygomatic 

 arch under which they pass must not only have a 

 certain degree of convexity, but it must be suffi- 

 ciently strong to support the action of the masseter. 



To enable the animal to carry off its prey when 

 seized, a corresponding force is requisite in the 

 muscles which elevate the head ; and this neces- 

 sarily gives rise to a determinate form of the ver- 

 tebrae to which these muscles are attached, ancj 

 of the occiput into which they are inserted. 



