1 1 2 Natural Theology. 



we are struck with admiration at the permanence 

 of the plan which appears through all the modifica- 

 tions. Some bones are lengthened, some are short- 

 ened, and some are indeed wanting ; but enough 

 are left to give an outline. The pectoral fin of the 

 first fish in the Silurian seas, in the dim geologic 

 ages, was the first sketch of the hand of man which 

 Nature introduced upon the globe. And from that 

 simple sketch she never varied ; but the plan became 

 more definite and perfect, and higher in its use, as 

 higher animals were introduced, till an organ was 

 produced that is a fit servant of the intelligence 

 I with which man is endowed. 



In the teeth of animals we have a marked adapta- 

 tion to the instincts and desires of the various spe- 

 cies. The Rodents, of which the beaver and squirrel 

 are well known types, have their cutting-teeth al- 

 most as hard as steel upon the front, and softer upon 

 the inside, so that constant use is sure to give them 

 a sharp, cutting edge. And because these teeth 

 are subjected to such constant wear, they are made 

 to grow continuously. We see here a need to be 

 supplied, and the structure of the tooth and the 

 unusual condition of growth are both combined to 

 secure the needed result. We referred to the early 

 introduction of the ball and socket joint in the 

 Echinus for the joining of his spines upon his shell. 

 The same animal has the teeth constructed on the 

 same plan as the Rodents, though they are five in 

 number, and move concentrically. 



In carnivorous animals, the teeth, in form and 



