OSTEOLOGY. 45 



THE DORSAL VERTEBRAE have large, heart-shaped bodies, flat 

 above and below. Laterally are demi-articular facets for heads 

 of ribs; long, strong, transverse processes, marked by facet, for 

 tubercle of rib; vertical articular processes, superior backward, 

 inferior forward; long, triangular, overlapping spinous process; 

 small, and nearly circular, spinal canal. 



The peculiar dorsal vertebra? are : first, which resembles 

 cervical, and have distinct facet for head of first rib, and half-one 

 for half of second head; tenth, eleventh, and twelfth, one facet 

 for head of rib ; and eleventh and twelfth, no facet on transverse 

 processes for tubercle of rib. 



THE LUMBAR VERTEBRAE are the largest, and have trans- 

 versely oval body, flat above and below; long, thin, transverse 

 processes, representing ribs; vertical processes interlocking with 

 adjacent vertebrae; large, triangular spinal canal. 



The last lumbar is peculiar in having body thicker in front, 

 shorter and stronger transverse process, and inferior articular 

 processes wider apart, and directed forward. 



Muscular attachments to atlas, ten rectus anticus minor, 

 rectus lateralis, rectus posticus minor, obliquus superior and 

 inferior, splenius colli, levator anguli scapula, interspinous, and 

 intertransverse. To axis, ten the last five of preceding, and 

 obliquus inferior, rectus posticus major, semi-spinalis colli mul- 

 tifidus spinse, scalenus posticus, and transversalis colli. 



To the remaining vertebrae are attached anteriorly ten (10) 

 muscles, and posteriorly twenty-two (22) [vide Spinal Muscles, 

 p. 107]. 



Development. The ossific centres for each vertebra are 

 three primary, one for the body and one for each side, and five 

 secondary opi pluses, as follows: one for tip of each spinous and 

 transverse process, and the remaining two are thin plates on 

 articular surfaces. 



The exceptions to this rule are: atlas, with two primary 

 centres and one epiphysis ; the axis, with three extra centres for 

 odontoid process; the seventh cervical, with one extra centre for 

 each transverse process, and the lumbar vertebrae, two additional 

 centres for tubercles. 



THE SACRUM is a large, wedu-e-sliaped l>one, base above, apex 

 below, with expanded lateral masses and ahe, composed of five 

 consolidated sacral vertebrae, and forming the posterior wall of 

 pelvis. 



The base articulates with the last lumbar vertebra. Its 

 anterior edge forms the i>roin(>iil<inj or xnrro-rrrtchral angle, on 

 each side of which is a smooth triangular surface, the ala. Be- 

 hind the articulating surface is the sacral canal, and on either 

 side are the superior processes. 



