BY W. J. McKAY. 919 



Pedicles : The pedicles arise from the lateral portion of the 

 superior surface of the centrum. They are very short anteriorly, 

 but longer behind, and run upwards and slightly outwards. 

 The external surface is grooved for the subvertebral rectus 

 muscle, while anteriorly the buttress of bone supporting the prezy- 

 gapophysis springs from its side. The anterior and posterior edges 

 are indented forming portions of intervertebral notches for the 

 exit of the spinal nerves. Where the posterior portion of the 

 pedicle joins the lamina the postzygapophysis is given off. 



LamincE : The laminae run upwards and inwards from the 

 pedicles to the mid-line ; at the same time they are produced 

 forwards and backwards to form the zygosphene and zygantram 

 respectively. The external surface of the lamina is excavated for 

 the rotatores dorsi muscles. The anterior edge is taken up by the 

 zygosphene ; the posterior is well marked and runs outwards into 

 the posterior edge of the first zygapophysis, while it is continued 

 internally into the neural spine. 



Neural spine : The neural spine springs from the junction of 

 the laminae in the mid-line. It is quadrilateral in outline. The 

 edge is sharp, and the tendons of the spinalis dorsi are inserted on 

 it. The anterior edge is likewise sharp, and gives attachment to 

 the interspinales. The posterior edge is marked by an excavation 

 in which the interspinales lie; The lateral sides of the spine are 

 broad and smooth, and from here the spinalis dorsi and multifidus 

 spinse arise, the former above, the latter below. 



Zygosphene : The zygosphene projects from the anterior borders 

 of the laminse as a well marked process. The superior surface is 

 convex, and gives attachment to a strong ligament which helps to 

 bind the vertebrae together. The lateral surfaces are bevelled 

 from above, downwards and backwards, forming facets for articula- 

 tion with the preceding zygantrum. 



Zyantrum : The zyantrum is formed by the expansion of the 

 laminse posteriorly. It presents two facets, which will be under- 

 stood by supposing a pyramidal piece to be excavated from the 

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