THE HOESE. 



41 



bral chain, thorax, and pelvis. It is gener- 

 ally called the spine, or back bone, and 

 extends from the occipital bone to the sac- 

 rum. The spine is divided into three 

 regions, denominated cervical, dorsal, and 

 lumbar. The spine, as a whole, exhibits 

 three surfaces and two extremities. The 

 surfaces are named superior, inferior, and 

 lateral. The superior sm-face is flat in the 

 region of the neck; in the back and loins 

 it offers a series of projections. The infe- 

 rior surface is more uniform, and the lateral 

 is very irregular. *. 



CERVICAL VERTEBRA. 



Q. How many cervical vertebree are 

 there ? — A. Seven. 



Q. What is the name of the first ? — A. 

 It is called atlas. 



Q. How does it differ from the rest? — A. 

 It has no superior spinous process nor body ; 

 the vertebral hole is larger than in the 

 others, and its transverse processes are very 

 broad. It has three pairs of foraminas : 

 one posteriorly, through which run the verte- 

 bral arteries ; and two anteriorly. 



Q. What is the name of the second cer- 

 vical vertebra ? — A. It is named dentata. 



Q. How is it recognized from the rest ? 

 — A. By its anterior projection, which in 

 the human subject resembles a tooth. 



Q. With what does this tooth-like pro- 

 cess articulate ? — A. It articulates with 

 the infero-posterior part of the ring of the 

 atlas. 



Q. Describe the third, fourth, and fifth 

 cervical vertebrte. — A. They possess the 

 genuine characters of cervical vertebrce, and 

 closely resemble each other; the third, how- 

 ever, has commonly a more elevated supe- 

 rior spine than either of the others, and is 

 narrower across the mesio-superior part of 

 the body (measuring from the roots of the 

 articular processes), which dimension in- 

 creases in the fourth, but is greatest in the 

 fifth. 



Q. What of the sixth vertebral — A. It 

 has no inferior spine ; and its transverse pro- 

 cesses are trifid, consisting each of three 

 eminences. 



6 



Q. What of the seventh 1—A. It is the 

 shortest, and in its general conformation re- 

 sembles the first dorsal. Its body, pos- 

 teriorly, presents two semilunar articulai 

 depressions, constituting a part of the socket 

 for the first rib. 



DORSAL VERTEBRA. 



Q. How many dorsal vertebrse are there? 



— A. Eighteen. 



Q. What is peculiar to the dorsal ver- 

 tebrae ? — A. They have each a body, spinous 

 process, and transverse process, and are 

 generally distinguished by the length, form, 

 and direction of their spines. 



Q. How is the first dorsal vertebrce dis- 

 tinguished from the rest? — A. By the 

 sharpness of its spinous, and singleness of 

 transverse, processes, and by the breadth of 

 its articulatory surfaces. 



Q. How do the articular depressions for 

 the insertion of the ribs differ in each bone? 



— A. They are less deeply marked, as we 

 proceed posteriorly. 



Q. How are the seventeenth and eight- 

 eenth distinguished from the rest? — A. 

 They have perfect articulatory depressions 

 on the bodies for the insertion of ribs. 



LUMBAR VERTEBRA. 



Q. How many lumbar vertebrae are 

 there? — A. Five. 



Q. How are the bodies of the lumbar 

 vertebrce distinguished from the dorsal? — 

 A. They are larger, contracted in the centre, 

 and their edges are more prominent. 



VERTEBRAL CANAL. 



Q. What is the form of the vertebral 

 canal? — A. In the cervical region it is ca- 

 pacious and semi-oval ; through the dorsal, 

 transversely oval and smaller. In the lum- 

 bar it is semi-circular, of less diameter than 

 the cervical and greater than the dorsal. 



Q. With what does the spinal canal con- 

 nect ? — A. Anteriorly, with the cranial 

 cavity ; posteriorly, with the sacral canal. 



PELVIS, SACRUM, AND TAIL BONES. 



We shall now consider the posterior 

 boundary of the trunk. 



