2O Anatomy of Skeleton 



The cruciate and occipito-odontoid ligaments are covered behind by the membrana 

 tectoria or occipito-axoid ligament, a broad thin band that extends to the basilar groove 

 on the occipital bone from the back of the body of the Axis : it has the spinal dura 

 mater in contact with it and attached to it, and it becomes continuous with the posterior 

 common ligament on the Axis. There are some variable lateral fibres of this sheet, 

 attached to the occipital behind the anterior condylar foramina. 



The capsules of the joints on the two first vertebrae are loose, and do not interfere 

 with the movements, save in the case of the occipito-atloid capsule and extension of 

 the head. There is, however, on the postero-internal aspect of the atlo-axoid joint a 

 strong accessory band that might conceivably help to limit rotation toward the opposite 

 side. The band is sometimes considered to be part of the lateral sheet of the membrana 

 tectoria. 



Detailed Consideration of Cervical Vertebrae. 



The anterior common ligament covers the bodies centrally, and on each side of 

 this are the prevertebral muscles. Take one of the middle members of the series and 

 observe that the central ligamentous area is raised and flattened, while the lateral 

 muscular areas are hollow and extend on to the fronts of the transverse (costal) pro- 

 cesses. Also notice that the size relation between the areas is not constant : as we 

 ascend the column the ligamentous area decreases in width, with a corresponding 

 increase in the muscular hollows. This indicates the increasing breadth of the ligament 

 from above downwards and shows plainly how it is only a narrow cord when it 

 reaches the anterior tubercle of the Atlas : because this tubercle is made by the 

 ligament, it has its tip directed downwards. 



The observant eye can easily read these facts on the column, to which the ligament 

 is attached strongly in the neighbourhood of the discs, but loosely on the remaining 

 front of the body. 



The muscular area, partly on body and mostly on the costal processes, presents 

 roughnesses for the attachment of the vertical portion of Longus colli : the oblique 

 portions of the muscle are inserted into the costal processes, and these usually show 

 ridges for the tendons of the lower oblique part on the front surfaces of the fifth and 

 sixth vertebras (Fig. ISA). The large upper hollows are occupied by the Rectus anticus 

 major in addition to the Longus colli, and the origin of this muscle by tendon is indicated 

 on the anterior tubercles of 3, 4, 5, and 6 C. V. The Atlas, viewed from the front, 

 presents the largest muscular hollow, altogether occupied by R. anticus major lying 

 on the bone, while the Longus colli comes to its attachment on each side of the base 

 of the anterior tubercle : it has already been seen that the direction of the anterior 

 tubercle is determined by the attachment of the anterior common ligament, but a 

 roughened area on its upper part shows where the anterior occipito-atlantoid ligament 

 continues the line of the common ligament to the skull. 



The third, fourth, fifth, and sixth vertebrae are the only ones possessing noticeable 

 anterior tubercles as terminations of their costal processes : these are the only segments 

 that have muscles attached here, and it seems not unlikely that not only the presence 

 of the tubercles, but also their direction, is determined by the muscular attachment. 

 Thus the lower oblique fibres of Longus colli, and the lower strong fibres of Scalenus 

 anticus, are inserted into the anterior tubercles of 5 and 6 C. V., and their downward 

 pull, only antagonised by the lower fibres of R. anticus major, may account for the 

 fact that these tubercles are at a lower level with regard to the transverse element 

 than are those of 3 and 4 C. V. In the latter vertebrae the upward pull is by stronger 

 fibres of the anterior Rectus and the upper oblique fibres of Longus colli, only 



