88 VERTEB RATED ANIMALS. 



those 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 ra- 

 dius and ulna, e and/. 



The humerus is a long cylindrical bone, with its up- 

 per 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. 



At its lower extremity the humerus is gradually ex- 

 panded, 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 el- 

 bow joint. 



The mechanism of the elbow joint, as well as the ac- 

 tion 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. 



Unity of design manifested in the constitution of the 

 Spines of Vertebrated Animals. It is a truth as won- 

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

 velopes, 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 1 What joint is formed by the 

 articulation of the head of the humerus ? What bones are articulated 

 with the lower end of the humerus 1 What is said of the unity of design, 

 as exhibited in the spines of various animals 1 



