CHAPTER III. 

 THE SKELETON. 



13. BY the skeleton is meant the hard framework of the 

 body. It consists of bones, cartilages, and ligaments. 



What is called the backbone, or, more properly, the verte- 

 bral or spinal column, may be said to be the central part of 

 the skeleton. It is composed of a series of bones called 

 vertebra, the fore parts or bodies of which, united by means 

 of discs of flexible tissue, constitute a pillar of support, while 

 what are termed the arches, lying behind this pillar, form a 

 protective cylinder round the spinal cord, have spinous and 

 transverse processes projecting from them, and glide one on 

 another by joints. There are twenty-four of these movable 

 vertebrae, the seven highest of which, belonging to the neck, 

 are called cervical, while the following twelve carry ribs and 

 are called dorsal, and the remaining five are termed lumbar. 

 They are succeeded by the sacrum and coccyx, which form 

 the lower part of the vertebral column, and will be further 

 alluded to. 



Springing from the dorsal portion of the vertebral column 

 are twelve pairs of ribs, which are further prolonged in front 

 by means of costal cartilages. The costal cartilages of the 

 upper seven pairs of ribs are prolonged forwards to the breast- 

 bone or sternum, to be fitted into its sides; those of the suc- 

 ceeding five pairs are each fixed to the cartilage next above; 

 while those of the eleventh and twelfth ribs are pointed, and 

 terminate in the muscular wall of the abdomen. The circles 

 formed by the ribs and parts with which they are connected 

 are called costal arches, while the series of ribs and costal 

 cartilages, together with the dorsal vertebrae and sternum, 

 constitute the thorax of the skeleton. 



14. Articulating with the upper end of the sternum, in tho 



