12 ELEMENTARY PHYSIOLOGY 



LESSON II 

 THE SKELETON. 



BONES OF THE TRUNK. 



HAVING briefly considered the general build of the body, we will 

 now study more particularly the nature of the skeleton. This 

 book deals exclusively with the structure and functions of the 

 human body; and, unless otherwise stated, the illustrations all 

 refer to man. Nevertheless, it must be remembered that the 

 structure of the human body is in all its broadest features similar 

 to that of many of the lower animals ; so much so, that a descrip- 

 tion of the human body may be illustrated by the dissection of 

 one of these animals. It is very desirable, therefore, that even 

 beginners in the study of human physiology should examine the 

 bodies or parts of such animals as can be conveniently procured. 

 Thus, a knowledge of the position and uses of the various parts 

 of the skeleton may be obtained by a thoughtful inspection of 

 the bones of a rabbit. Or the student may easily prepare for 

 himself a complete skeleton of any small animal by burying the 

 body just beneath the surface of a wet soil. In a few weeks the 

 flesh will have decomposed to such an extent that the skeleton 

 may be washed clean in running water, and afterwards bleached 

 by exposure to the sun. 



We shall first study the backbone, or central portion of the 

 skeleton, and the bones directly connected with it. 



The backbone, vertebral column, or spinal column is com- 

 posed of a series of bones called vertebra (Lat. verto, I turn), and 

 forms a kind of axis with which all the other parts of the skeleton 

 are connected. The base of the skull rests on the uppermost of 

 these vertebras, and the lower portion of the column is wedged in 

 between the bones of the hip. The backbone is usually said to 

 consist of thirty-three bones, but only twenty-four of these are 

 jointed in such a manner as to be movable on each other, viz. 

 the bones of the neck, back, and loins. The lower part of the 

 column consists of nine bones fused together. The seven highest 

 vertebras belong to the neck, and are called the cervical vertebrae 

 (Lat. cervix, the neck). The next twelve are called the dorsal 

 vertebrae (Lat. dorsum, the back) ; these belong to the back and 

 support the ribs. The remaining five movable vertebrae belong 

 to the loins, and are called the lumbar (Lat. lumbus, the loin) 

 vertebrae. 



The lowest lumbar vertebra rests on the broad surface of a 



