BY W. J. McKAY-. 929 



vertebra, while its inferior portion is slightly convex, and glides 

 over the surface between the two facets of the transverse process. 

 The process springs from the upper portion of the extremity, and 

 is continuous with the posterior surface of the shaft. It runs 

 upwards and backwards, and gives attachment to the innermost 

 bundles of the external intercostal muscles ; while the superior 

 vertebro-costal ligament, running forwards and outwards round 

 the superior surface of this process, thus prevents rotation for- 

 ward of the upper and inner portion of the rib. 



The Shaft : The shaft is prismatic in shape and presents an 

 anterior, posterior, and inferior surface, together with three borders. 



Anterior surface : To the upper portion of the inner third of 

 the anterior surface are attached the levatores costarum externi ; 

 while to the lower portion of this inner third and to the whole of 

 the outer two-thirds are attached the external intercostals. 



Posterior surface : The posterior surface, (which if continued 

 internally would end in the process described above) gives attach- 

 ment to the external intercostals. 



Inferior sihrface : The inferior surface is more rounded than the 

 preceding ones, but it is not well defined from the posterior surface, 

 except internally. The external intercostals arise from here as 

 well as from the posterior surface. 



There are three borders, a superior, anterior, and posterior. 



Superior border : The accessory portion of the sacro-lumbalis 

 column arises at the junction of the inner two-fifths with the outer 

 three-fifths; while immediately external to this we have the sacro- 

 lumbulis inserted, and the pretrahentes costarum superiores, and 

 the external oblique arising. The pretrahentes superiores cover the 

 middle third, and are inserted at the j unction of this with the outer 

 third over which the pretrahentes inferiores run. 



A^iterior horder : The anterior border when followed inwards 

 is seen to end in a tuberosity which gives attachment to the 

 levatores costarum interni, and the inferior vertebro-costal liga- 

 ment. The outer third of this border gives origin to the retrahentes 

 costarum. 



