$4 VEllTEbKATED ANIMALS. 



which make no such use of their feet, are without it, as 

 the horse and sheep. 



The bones of the arm are the humerus, d, and the 

 radius, and ulna, e andy. 



239. The humerus is a long cylindrical bone, with its 

 upper end articulated to the scapula, forming the shoulder 

 joint. - At the point of articulation, the extremity is en- 

 larged into a round, smooth head, which is admitted into 

 the glenoid, or shallow cavity of the scapula, where it is 

 strongly secured by ligaments, but in such a manner as to 

 allow it motion in all directions. 



240. At its lower extremity, the humerus is gradually 

 expanded, for the articulation of the two bones of the fore- 

 arm, the radius and ulna, both of which are connected 

 with this bone at their upper extremities, forming the 

 elbow joint. 



241. The mechanism of the elbow joint, as well as the 

 action of the muscles on the radius and ulna, together with 

 the mechanism and wonderful powers of the hand, will be 

 reserved for another place, while we proceed to an 

 .account of the spines of other vertebrated animals 



The whole number of bones in the human species 

 amount to 240. 



242. Unity of design manifested in the Constitution of 

 the Spines of Vertebrated Mnimals. It is a truth, as won- 

 derful as it is instructive, which the study of nature de- 

 velops, that although the Creator had almighty power 

 and infinite wisdom, and might, therefore, have varied 

 his plans, and executed his designs, in an infinite number 

 of ways, in the construction of the different races of 

 animals, that we still find an economy of design, and a 

 unity of plan in the general construction of the frame- 

 work, or foundations of the grand divisions of animals, 

 which prevails throughout all the orders, or sub-divisions, 

 however different the destinies, or habits of the distinct 

 races may be from each other. Reasoning and judging 

 on this subject as we do with respect to the arts of man, 



What, are the bones of the arm called ? What joint is formed bv the 



