364 HEAD AND NECK 



as it is developed around the continuation of the chorda 

 dorsalis from the dens to the basis cranii, is a structure of 

 considerable morphological interest. The anterior part of 

 the apical ligament is a flat and weak band which is 

 attached above to the anterior margin of the foramen magnum 

 at the same point as the posterior portion. Below, the two 

 portions are separated by an interval filled with cellular 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. 145). These are very powerful 

 bands which spring, one from each side of the summit of 

 the dens. They pass laterally and slightly upwards to be 

 attached to the medial aspect of the condyloid eminences of 

 the occipital bone. They 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 chambers. 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 

 passes round the teeth and gums, is a mere fissure-like space, 

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

 part of the mouth that the parotid ducts open (p. 261). 



