SKELETO.V OF VERTERRATA. 281 



ber. While in animals of llic inferior orders, which arc 

 possessed of extremities, we find a considcrahle number of 

 legs; in all the animals comprised in the class of true insects 

 nature has limited the number to six; and in the vertebrata 

 it never exceeds four. As in insects, we observed that all 

 the legs are divided into the same number of parts, so we 

 find among quadrupeds a striking correspondence in the 

 bones of the fore and the hind extremities. Both the one 

 and the other are connected with the spine by the interme- 

 dium of large and broad bones, which are intended to serve 

 as a basis for their more secure attachment, and for giving, 

 at the same time, extensive and advantageous purchase to 

 the muscles, which are to move the limbs. The two bones 

 by which the anterior extremity is connected with the 

 trunk are the hlade-hone, or Scapula, (u,) which sends out 

 a process called the coracoid bone; and the collar-hone, or 

 the Clavicle,'^' which extends from the scapula to the ster- 

 num. The corresponding connecting bones of the posterior 

 extremity are three in number, and constitute, together with 

 the part of the spine to which they are attached, what is 

 called the Pelvis (p.) The part of the spine which is thus 

 included in the pelvis, is termed the Sacrum. In its com- 

 plete state of ossification it is a single bone; but it was ori- 

 ginally composed of a number of separate vertebras, which 

 have afterwards become consolidated into a single bone, and 

 which bear the marks of having been compressed from be- 

 hind forwards during their growth, so^that they could only 

 expand laterally. The vertebrae which succeed to these, 

 and which are not consolidated with the sacrum, compose 

 what is called the os coccygis, (q,) or more properly the 

 coccygeal verlehrx: when they are sufliciently numerous to 

 compose a tail, they come under the denomination of caudal 

 vertebrx. The three bones of the pelvis, are the iliu7?i, the 



• This bone does not exist in the skeleton of the hog-: but its form and 

 connexions with the sternum and scapula, in the liuman skeleton, arc slio\sn 

 in Fig-. 182, where s is the sternum; c, the clavicle; h, the scapula; a, the 

 acromion; k, the coracoid process; and g-, the glenoid cavity for the articula- 

 tion of the humerus. 



Vol. I. 36 



