THE VAGO-ACCESSORY MUSCLES. 495 



The relation of many of the bony points to the overlying soft parts has been 

 described (page 246). 



The shape of most of the muscles cannot be separately distinguished. Com- 

 parison of a skull with a partially dissected head will show, however, that over the 

 vault of the cranium from the supra-orbital ridges to the nucha the general shape of 

 the skull determines the surface form during life, the flattened muscles and aponeu- 

 rosis closely conforming to it. In the temporal regions, in spite of the deep bony 

 fossa, the triangular muscle and the accompanying fat (page 491) make the surface 

 in vigorous, well-nourished persons slightly convex. The outlines of the muscle can 

 be seen when it is in contraction, especially the portion anterior to the hairy scalp. 



On the face the characteristics that distinguish the individual are due largely 

 to the presence of muscles and of subcutaneous fat. The edge of the orbit and the 

 naso-frontal junction are covered and given rounded outlines by the orbicularis 

 palpebrarum and the pyramidalis nasi. The muscles running from the malar bone 

 and maxilla to the upper lip aid the buccinator and the fat of the cheek in fiUing up 

 the great hollows beneath the malar prominences. The orbicularis oris gives shape 

 and expression to the mouth. The masseter fills out the posterior portion of the 

 cheek and becomes visible in outline when in firm contraction, especially the vertical 

 anterior border, just in front of which the facial artery crosses the inferior maxilla. 



As nearly all the facial muscles have fibres of insertion into the facial integument, 

 their influence upon expression and upon the creases and folds that become perma- 

 nent as "wrinkles," "crows' feet," etc., is apparent. 



III. THE VAGO-ACCESSORY MUSCLES. 



The muscles supplied by the glosso-pharyngeal, vagus, and spinal accessory 

 nerves may be grouped together both on account of their relations in the adult and 

 on account of the intimate relations which exist between the three nerves. The 

 glosso-pharyngeal and vagus correspond to the posterior branchial arches, the glosso- 

 pharyngeal to that represented in the adult by the greater cornu of the hyoid bone 

 and the vagus to those represented by the laryngeal cartilages. Consequently we 

 find the muscles supplied by these nerves to be those associated with the pharynx 

 and larynx, one of the muscles of the soft palate, the levator palati, being also 

 included in the group. The pharyngeal muscles, for the most part, are supplied from 

 the pharyngeal plexus, into which fibres from both the glosso-pharyngeal and vagus 

 nerves enter. The laryngeal muscles, however, are supplied by branches coming 

 directly from the stem of the vagus nerve. 



The spinal accessory nerve stands in such intimate relations with the vagus that 

 its nucleus of origin may well be regarded as an extension of that of the vagus, and 

 by the union of a portion of its fibres with those of the vagus to form a common 

 trunk opportunity is afforded for its fibres to participate in the formation of the 

 pharyngeal plexus, and there is evidence pointing to the origin of the fibres of the 

 inferior laryngeal nerve, which supplies the majority of the laryngeal muscles, from 

 the spinal accessory nucleus. 



In addition, however, to its participation in the supply of the pharyngeal and, 

 possibly, the laryngeal muscles, the spinal accessory also innervates the trapezius 

 and sterno-mastoid muscles, and these, on account of their relations, must constitute 

 a subgroup distinct from the other vago-accessory muscles. 



(a) THE MUSCLES .OF THE PALATE AND PHARYNX. 



Palato-pharyngeus. 

 Constrictor pharyngis superior. 

 Constrictor pharyngis medius. 

 Constrictor pharyngis inferior. 



I. Stylo-Pharyngeus (Figs. 502, 509). 



Attachments. ^The stylo-pharyngeus arises from the inner surface of the 

 styloid process near its base. It is directed downward, the glosso-pharyngeal nerve 



