ON DESIGN IN ANIMAL BODIES. 197 



out of the system of the animal body, but, on the 

 contrary, it participates in those laws that govern 

 living matter. It is continually undergoing the 

 changes of deposition and absorption, under the 

 influence of blood-vessels and absorbing vessels ; 

 by which means it growls with the growth of the 

 soft parts. 



In fishes, which live in an element that supports 

 the weight, the bones have a very large propor- 

 tion of elastic cartilage in their composition, and 

 some have so little of the phosphate of lime in 

 their bones as to be denominated cartilaginous 

 fishes. Indeed, in the higher classes of animals 

 which live upon land, there is in the different 

 bones a finely-appropriated union of earth, cartil- 

 age, and fibre, to give them the due proportion of 

 resistance, elasticity, and toughness. Not only is 

 the bone of each class of animal peculiar in the 

 proportion of the ingredients, but each bone of 

 the skeleton, as of man, has a due proportion of 

 earth, and cartilage, and fibre to suit its oflice. 

 The temporal bone, in which the ear is situated, 

 is as dense as marble, (it is called os petrosu??i,) 

 and of course is suited to propagate the vibration 

 of sound : the heel-bone, or the projection of the 

 elbow, on which the powerful muscles pull, is, on 

 the other hand, fibrous, as if partaking of the na- 

 ture of a tendon or rope ; whilst the columnar 

 bones, which support the weight, have an inter- 

 mediate degree of density, and an admirable 

 form, as we shall see presently. 

 18* 



