Vertebral Column 



21 



antagonised by weak upper fibres of Scalenus anticus. The downward direction of the 

 brachial nerves may also affect the fifth and sixth processes. The Rectus and the upper 

 oblique fibres are frequently fused at their attachments, so that no separate markings 

 are found on the bone ; but occasionally separate markings are seen for the oblique 

 fibres, internal to the tubercle. Observe that the posterior tubercles project beyond 

 the level of the articular masses, whereas the anterior ones do not do so. 



The lateral view of the cervical column discovers differences in the transverse 

 processes below the Axis. They are sufficiently striking from the surface (Fig. 16) 

 and can be summarised as follows. Third vertebra has its costal process small and 

 on an altogether higher level than the true transverse element, a very oblique costo- 

 transverse bar, and a very narrow and 

 shallow neural groove. 



In the fourth the obliquity is not so 

 marked and the groove is deeper, with a 

 higher anterior tubercle. 



In the fifth the costo-transverse bar 

 is more nearly horizontal, and the groove 

 is wider and deeper in correspondence with 

 the larger size of the anterior division of 

 the fifth nerve. 



In the sixth the groove is extremely 

 wide, a character that distinguishes this 

 from the other vertebrae, especially when 

 taken in conjunction with its large anterior 

 tubercle, ridged in front. This tubercle is 

 occasionally much increased in size, forming 

 the carotid tubercle or Chassaignac's tubercle. 



In the seventh the anterior element is 

 very small and may be incomplete, and has 

 no muscle attachment : the posterior 

 element, on the other hand, is compara- 

 tively massive, and roughened at its ex- 

 tremity for the lower scalene and levator 

 costae fibres. It can be appreciated that 

 the small size of the costal element affords 

 room for the vertebral artery to run up to 

 the sixth transverse process : the articu- 

 lated bones will show that the artery must 



lie just in front of the seventh costal element and the seventh nerve that runs 

 behind it, and therefore immediately lateral to the Longus colli. 



Examine the neural groove in any of the middle or lower segments, and notice 

 that the issuing nerve must pass behind the vertebral artery in its course. This is 

 the anterior primary division of the nerve corresponding in number * with the ver- 

 tebra : the posterior primary divisions arise in the intervertebral foramen and turn 

 back over the transverse element and round the articular process, making a slight 

 groove on the third segment (see Fig. 17). 



The first two cervical nerves differ from all other spinal nerves in issuing behind 

 the articular masses. The explanation is that the articular masses concerned are 



* Each cervical nerve is above its vertebra : the eighth is therefore above I D.V. and below 7 C.V. 

 So the first dorsal nerve is below its vertebra, as are the remaining spinal nerves. 



m 



FIG. 16. Cervical vertebrae articulated to show 

 the transverse processes for comparison. 



