56 



OSTEOLOGY. 



Fig. 21. Lateral View of Spine. 



1st Cervical 

 orAtiut. 



7-1 



anteriorly; the convexity of the lower 

 three vertebras being much greater than 

 that of the upper ones. The pelvic curve 

 commences at the 'sacro- vertebral articula- 

 tion, and terminates at the point of the 

 coccyx. It is concave posteriorly. These 

 curves are partly due to the shape of the 

 bodies of the vertebras, and partly to the 

 intervertebral substances, as will be ex- 

 plained in the Articulations of the Spine. 



The spine has also a slight lateral 

 curvature, the convexity of which is di- 

 rected toward the right side. This is 

 most probably produced, as Bichat first 

 explained, from the effect of muscular 

 action ; most persons using the right arm 

 in preference to the left, especially in 

 making long-continued efforts, when the 

 body is curved to the right side. In 

 support of this explanation, it has been 

 found, by Beclard, that in one or two in- 

 dividuals who were left-handed, the lateral 

 curvature was directed to the left side. 



The spinal column presents for exami- 

 nation an anterior, a posterior, and two 

 lateral surfaces; a base, summit, and ver- 

 tebral canal. 



The anterior surface presents the bodies 

 of the vertebrae separated in the recent state 

 by the intervertebral disks. The bodies 

 are broad in the cervical region, narrow 

 in the upper part of the dorsal, and broadest 

 in the lumbar region. The whole of this 

 surface is convex transversely, concave from 

 above downwards in the dorsal region, and 

 convex in the same direction in the cervical 

 and lumbar regions. 



The posterior surface presents in the 

 median line the spinous processes. These 

 are short, horizontal, with bifid extremi- 

 ties in the cervical region. In the dorsal 

 region, they are directed obliquely above, 

 assume almost a vertical direction in the 

 middle, and are horizontal, like the spines 

 of the lumbar vertebras, below. They 

 are separated by considerable intervals in 

 the loins, by narrower intervals in the 

 neck, and are closely approximated in 

 the middle of the dorsal region. Oc- 

 casionally one of these processes deviates 

 a little from the median line, a fact to 

 be remembered, as irregularities of this 

 sort are attendant on fractures or dis- 

 placements of the spine. On either side of 

 the spiuous processes, extending the whole 

 length of the column, is the vertebral 

 groove, formed by the lam! nas in the cer- 



