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 anastomose not only with one another, but also with the 

 fibres of adjacent strata, as is shown by the rough surface which is 

 left when one set of fibres is removed from the underlying set. 



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

 spinal 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 suffice to take a segment con- 

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



Fig. 15. 



TWO COSTO-VERTEBRAL, AND TWO 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 costotransverse 

 ligament; 5. Intervertebral disc, covered by 0. 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 costo-central joint. The tubercle articulates 

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

 of the vertebra to which the head is articulated. This is the costo- 

 transverse joint. 



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

 vertebral and interarticular, and two svnovial sacs. 



