Vertebral Column 



MasToidpr. 



Tr.proc. 



extend out on to the transverse process, and is limited below by an ill-defined promi- 

 nence continuous with the front limb of the transverse process. Below and internal 

 to the prominence is a hollow which is filled by Rectus anticus major without affording 

 origin to it. 



The prominence just mentioned, shown in Figs. 16 and 19, answers to the anterior tubercle 

 of the transverse processes lower down. The modifications consequent on the growth of the neuro- 

 central articulations in the upper two vertebrae are shown schematically in Fig. 21. In the drawing 

 the right-hand side indicates the fundamental principle that is common to the cervical segments, 

 with the modifying factor, while the result is 

 shown on the left-hand in each figure. The 

 first figure represents the typical state, with a 

 costal process (a), a tran verse process (b), and 

 a costo-transverse bar (c). Articular processes 

 can be neural (x) or neuro-central (y). In the 

 typical cervical region they are neural, and lie, 

 therefore, on the neural arch at the base of 

 the transverse element, leaving the costal pro- 

 cess clear. The second figure shows how, in 

 the Axis, the upper neural articulation fails, 

 and the neuro-central one enlarges, spreading 

 outwards as shown by the shaded area, so that 

 it covers the costal process and causes the 

 course of the arterial canal to be turned out- 

 wards ; thus the condition already noted in 

 the Axis is attained. The last drawing shows 

 how a comparable condition is reached in the 

 Atlas without much change in the direction of 

 the foramen, because the articular surface is 

 not so broad. Thus the costal process can be 

 looked on as buried by the articular masses in 

 the upper bones, and the partly-suppressed 

 tubercle is all that remains to indicate its 

 position, while the anterior boundary of the 

 arterial foramen in these bones is really the 

 costo-transverse bar. So the nerves (N) are 

 seen to issue in corresponding and similar rela- 

 tions on all the bones. 



The transverse process of the atlas FlG 22 _ To show ^~ Mtxtiat relations of tne 

 (Fig. 15) has an external border that 

 shows a sharp lower ridge : this ridge 

 affords insertion to the aponeurosis of 

 Splenius colli (S), and the concave sur- 

 face internal to it, on the lower surface 

 of the process, is roughened for the insertion of the Inferior Oblique. Above the 

 ridge, on the upper aspect, are two impressions for Superior Oblique (S.O.) and 

 Levator anguli scapulae (L.A.S.), the latter reaching the front corner of the process 

 and the former extending from the posterior corner to the arterial groove. The 

 Rectus lateralis has a faint marking behind and internal to the Levator, extending 

 along the front limb of the process to the slight groove that lodges the anterior 

 primary division of the suboccipital nerve. The nerve runs forward round the outer 

 side of the articular mass (Fig. 20) lying deep to the inner border of the artery, and 

 emerges between the Rectus lateralis and anticus minor, thus lying immediately 

 behind the carotid sheath : after giving branches it turns down in front of the trans- 

 verse process to join the next nerve. The carotid sheath is altogether in front of the 



transverse process (tr. proc.) of the atlas. The 

 posterior belly of Digastric and Sternomastoicl 

 are represented as transparent, thus exhibiting 

 the Rectus lateralis and eleventh nerve related 

 to the process. This is the only transverse 

 process which projects beyond the vein. 



