JOINTS OF THE NECK 277 



margin of the foramen magnum at the same point as the 

 posterior portion. Below, the two portions are separated by 

 an interval filled with areolar tissue, and the anterior part is 

 attached to the dens immediately above its articular facet for 

 the anterior arch of the atlas. 



Ligamenta Alaria (Fig. 104). The alar ligaments are very 

 powerful bands which spring, one from each side of the 

 summit of the dens. Each passes laterally and slightly up- 

 wards to be attached to the medial aspect of the corre- 

 sponding condyloid eminence' of the occipital bone. The 

 alar ligaments limit rotation of the head, and in this they are 

 aided by the accessory atlanto-epistropheal ligaments. 



Movements. Nodding movements of the head are permitted at the 

 atlanto-occipital articulations. Rotatory movements of the head and atlas 

 around the dens, which acts as a pivot, take place at the atlanto- 

 epistropheal joints. Excessive rotation is checked by the alar ligaments. 



MOUTH AND PHARYNX. 



The dissectors must now return to the anterior part of the 

 skull, which had been laid aside while the dissection of the 

 prevertebral region was being carried on. The mouth and 

 pharynx should engage their attention in the first instance. 



Mouth. The mouth is the expanded upper part of the 

 alimentary canal which is placed in the lower part of the 

 face, below the nasal cavities. Its cavity is controlled by 

 muscles which are under the influence of the will, and it 

 is separable into two parts : a smaller external part, termed 

 the vestibule, which is bounded externally by the lips and 

 cheeks, and internally by the teeth and gums; and a large 

 part, the mouth proper, which is placed within the teeth. 



The mucous lining of the mouth should be thoroughly cleansed, and 

 the two subdivisions of the cavity examined through the oral fissure. 



Vestibulum Oris. The vestibule of the mouth, which 

 lies outside the teeth and gums, is a mere fissure-like space, 

 except when the cheeks are inflated with air. It is into the 

 vestibule of the mouth that the parotid ducts open (p. 164). 

 Above and below, it is bounded by the reflection of the 

 mucous membrane from the lips and cheeks on to the 

 alveolar margins of the maxillae and mandible. Anteriorly, 

 it opens upon the face by means of the oral fissure ; whilst 



