DISSECTION OF THE BACK AND THORAX. 



135 



superficial fibres ; and the obliquity of these increases until the inner 

 surface of the wall is reached, where the fibres have a degree of obliquity 

 equal to the most external fibres. The fibres of the same stratum anas- 

 tomose not only with one another, but also with the fibres of adjacent 

 strata, as is shown by the rough surface wliich is left when one set of 

 fibres is removed from the underlying set. 



Birections.—The joints and ligaments of the dorso-lumbar part of the 

 spjnal column and of the ribs must now be dissected. The ligaments of 

 the lumbar region will be exposed by carefully removing from the sur- 

 face of the bones the remains of muscles and other textures already 

 examined. The whole of the dorsal region need not be dissected in 

 order to expose the ligaments, but it will suflice to take a segment con- 

 taining four or five vertebrfe with their costal articulations intact. The 



Fig. 15. 

 two costo-vertebral, and ivvo intervertebral joints, viewed from below. 



1. Attachment of costo-vertebral (stellate) ligament to intervertebral disc; 2. and 3. Attachments 

 of the same ligament to the anterior and posterior vertebral bodies ; 4. Posterior costo-transverse 

 ligament ; 5. Intervertebral disc, covered by ty. the inferior common ligament. 



articulations of the costal cartilages to the sternum are to be examined 

 on the part of the thorax removed for the display of the triangularis 

 sterni muscle. 



ARTICULATIONS OF THE RIBS. 



Each rib is articulated to the spinal column at two points, viz., 

 by its head, and by its tubercle. The head is received into a cup- 

 like cavity formed by two adjacent vertebral bodies and the disc that 

 unites them. This is the aosfo-central joint. The tubercle articulates 

 with the flat facet on the transverse process belonging to the posterior of 

 bhe vertebrae to which the head is articulated. This is the costo-trans- 

 jerse joint. 



Costo-Cbntral Joint. This possesses two ligaments — the costo- 

 vertebral and interarticular, and two synovial sacs. 



