78 SKELETON. 



Unfortunately, ' the minuteness with which the skeleton is 

 described has been decried as useless, but the zealous and rea- 

 sonable student ought to bear in mind that the only-rational 

 plan of reducing a dislocated joint must depend upon a proper 

 knowledge of its articular faces; that many of the great phe- 

 nomena of life depend essentially upon the arrangement of the 

 skeleton; that locomotion is inseparably connected with it; 

 and that, in short, it has a bearing upon almost every animal 

 operation. With these facts impressed upon him, he will be 

 prepared to give the history of the skeleton a full and perfect 

 attention. 



CHAPTER J. 



THE TRUNK. 



THE trunk is constituted by the Spine, the Thorax, and the 

 Pelvis. 



SECT. I. THE SPIKE. 



The spine, (Columna Vertebralis, Rachis,) is placed at the 

 posterior part of the trunk, and extends from the head to the 

 inferior opening of the pelvis. It consists of twenty-eight or 

 nine distinct pieces, of which the upper twenty-four are true, 

 or moveable vertebrae. The twenty-fifth is the sacrum, or the 

 pelvic vertebra, which is fixed; and the remainder are the 

 caudal vertebrae or the coccyx. 



On the posterior face of the spine, each of the true vertebrae 

 is seen to contribute, by a long process, to that ridge which is 

 so readily felt beneath the skin, and from which, probably, the 

 name of spine was derived. The spine increases gradually in 

 size from the first to the last true vertebra. The upper part 

 of the sacrum is extended laterally much beyond the latter, 

 afterwards the spine diminishes abruptly to the extremity of 

 the coccyx. The spine has several curvatures, which are best 

 marked in the erect position. For example, the lower part of 

 the cervical portion is convex anteriorly, and concave behind 

 the thoracic part is concave in front,, and convex behind the 



