30 



BOTVES OP THE CRANIUM. 



process is an intervertebral notch. The inferior extremity presents 

 a small oval surface which articulates with the coccyx ; and on 

 each side a notch, which with a corresponding notch in the upper 

 border of the coccyx forms the foramen for the transmission of the 

 fifth sacral nerve. 



Developement. By twenty-one points of ossification ; five for each 

 of the three first pieces, viz. one for the body, one for each lateral 

 portion, and one for each lamina ; and three for each of the two 

 last, viz. one for the body, and one for each lateral portion. 



Articulations. With four bones ; the last lumbar vertebra, ossa 

 innominata and coccyx. 



Attachment of Muscles. To seven pairs ; in front the pyriformis, 

 O7i- the side the coccygeus, and behind the gluteus maximus, latissi- 

 mus dorsi, longissimus dorsi, sacro-lumbalis, and multifidus spin. 



The COCCYX (xoxxug cuckoo, from resembling a cuckoo's beak) is 

 composed of four small pieces, which form the caudal termina- 

 tion of the vertebral column. The superior piece is broad, and ex- 

 pands laterally into two transverse processes : it is surmounted by 

 an oval articular surface and two cornua ; the former to articulate 

 with the apex of the sacrum, and the latter with the sacral cornua. 

 The three latter pieces diminish in size from above downwards, and 

 are frequently consolidated into a single bone. 



Developement. By/bwr centres, one for each piece. 



Articulations. With the sacrum. 



Attachment of Muscles. To three pairs, and one single muscle : 

 gluteus maximus, coccygeus, posterior fibres of the levator ani and 

 sphincter ani. 



OF THE SKULL. 



The skull, or superior expan- 

 sion of the vertebral column, is 

 divisible into two parts, the 

 cranium and the face ; the former 

 being adapted by its form, struc- 

 ture, and strength to contain and 

 protect the brain, and the latter 

 the chief organs of sense. 



The CRANIUM is composed of 

 eight separate bones ; viz. the oc- 

 cipital, two parietal, frontal, two 

 temporal, sphenoidal, ethmoidal. 



OCCIPITAL BONE. This bone is 

 situated at the posterior part and 

 base of the cranium. Itistrapezoid 

 in form, and divisible into two sur- 

 faces, four borders, and four angles. 



* The external surface of the occipital bone. 1. The superior semicircular ridge. 

 2. The occipital protuberance. 3. The spine. 4. The inferior semicircular ridge. 5. 



