SKELETON IX GENERAL. 3 



which are originally distinct becoming united together as the process of 

 ossification proceeds. The following is an enumeration of those usually 

 reckoned as distinct in middle life : 



Single Pairs of T 4. , 

 Bones. Bones. 

 The spinal column consists of twenty -four free vertebrae, 



the sacrum, and the coccj-x ..... 26 26 



The skull consists of twenty-two bones : of these eight are 



cranial, viz., four single bones, the occipital, frontal, 



ethmoid and sphenoid ; and two pairs, the parietal 



and temporal. Fourteen are facial, viz., two single 



bones, the vomer and inferior maxillary bone ; and 



six pairs, the nasal, lacrymal, superior maxillary, 



malar, palatal, and turbinated .... 6 8 22 



There are twelve pairs of ribs, a sternum, and a hyoidbone 2 12 26 



The superior extremities consist each of a clavicle and 



scapula, humerus, radius, ulna, eight carpal bones, 



five metacarpal, and fourteen digital ... 32 64 



The inferior extremities consist each of a pelvic bone, 



femur, patella, tibia, fibula, seven tarsal bones, five 



metatarsal, and fourteen digital .... 31 62 



34 83 200 



Besides the bones above enumerated, there exist, likewise, three pairs of auditory 

 ossicles, and, in addition to the patella, various smaller bones called sesamoid. The 

 auditory ossicles, though enclosed within the temporal bones, may be considered as 

 belonging to the skeleton. The sesamoid bones are only accessories to the tendons in 

 which they are developed. 



Fig. 1. FIRST DORSAL VERTEBRA, FIRST RIB Fig. 1. 



AND CARTILAGE, AND UPPER PART OF THE 

 STERNUM, SEEN FROM ABOVE, GIVING A VIEW OF 

 A SEGMENT OF THE VERTEBRATE SKELETON. ^ 



C, body or centre ; N, vertebral ring or 

 neural arch ; V, cavity of the chest enclosed by 

 the ribs or visceral arch. 



The segments of the skeleton are BO 

 disposed as to surround or partially en- 

 close two cavities of unequal size the 

 neural and visceral. The neural cavity, 

 comprehending the cranium and vertebral 

 canal, is of great width in the head, and 

 comparatively small in the rest of its 

 length : it is nearly completely bounded 

 by bony walls in its whole extent. The visceral cavity, placed in front of 

 the vertebral column throughout its length, is only imperfectly represented 

 in the head by spaces enclosed by the bones of the face : its walls, which 

 are very incomplete, are most perfect in the thorax and pelvis, and leave 

 large open spaces in the regions of the neck and abdomen. In these several 

 regions, the relative position of the walls of the neural and visceral cavities 

 and of their contained viscera remains the same. 



I. THE VERTEBRAL COLUMN. 



The vertebral column may be considered as the foundation of the 

 skeleton, not only because it exists in all animals which possess an osseous 

 system, but because it is the centre round which the other parts are developed 



B 2 



