286 MUSCLES OF THE HEAD AND NECK. 



the hypoglossal nerve, the 'V^^lartonian duct, and the gustatory nerve. It covers 

 the genio-glossus and the origin of the middle constrictor of the pharynx, 

 together with the lingual artery and glosso-pharj-ngeal nei-ve. 



Variety. — Triticco-<ilossm (Bochdaiek). This is a small muscle which arises 

 from the cartilago triticea in the posterior th.^TO-hyoid ligament, and passes 

 upwards and forwards to enter the tongue along with the posterior part of 

 the hyo-glossus. It always lies behind the lingual artery. 



The stylo-glossns, the shortest of the three muscles \yhicli spring 

 from the styloid process, arises from that process not far from its point, 

 iind from the stylo-maxillary ligament, to which in some cases the 

 o-reater number of its fibres are attached by a thin aponeurosis : pass- 

 in"- forwards and slightly downwards, it is inserted along the side and 

 under part of the tongue as far as the tip, its fibres decussating, and 

 becoming blended with those of the hyo-glossus and palato-glossus 

 muscles. 



IicJntioii.9. — This muscle lies deeply beneath the parotid gland, and is crossed 

 by the gustatory nerve. 



Varictifx. — The ■wylo-f/Io.'.-sys ("Wood) is a small accessory slip, which iisually 

 comes from the angle of the lower jaw. but has also been seen coming from the 

 stylo-maxUlary ligament. Occasionally the whole muscle arises from one of 

 these points. A very rare origin has been noted by Gruber from the external 

 meatus. Albinus and Bohmer have noted entii'e absence of the muscle, and 

 various anatomists have seen it double. 



Nerves. — The muscles of this group are all supplied with branches from 

 the hypoglossal or motor lingnaB nerve. 



Actions.— The genio-glossus muscle has a Complicated action, one part pro- 

 truding and another retracting the tongue, while a third depresses the middle 

 portion of the organ. Protrusion is effected by contraction of its posterior, and 

 retraction by contraction of its anterior fibres, while the middle part, or nearly the 

 whole muscle, acts as a depressor. In deglutition the stylo-glossus muscle raises 

 the side of the tongue spasmodically backwards and upwards, while the hyo- 

 glossus opposes that action. In other circumstances the first muscle assists in. 

 f omaing a hollow, and the second a convexity on the dorsum of the tongue. 



MUSCLES OF THE PHARYNX AND SOFT PALATE. 



The Pharynx, the dilated upper part of the alimentary tube, 

 extending from the base of the skull to the oesophagus, presents at the 

 sides and back a continuous wall, in great part formed and supported 

 by distinct muscles resting posteriorly on the vertebral column, and is 

 open in front towards the nasal cavity, the mouth, and the laiynx. 



The CONSTRICTORS OF THE. PHARYNX are three thin expanded 

 muscles which invest the pharyngeal wall, overlapping one another 

 from below upwards, so that the lowest is most superficial. 



The inferior constrictor mu.scle arises from the side of the cricoid 

 cartilage, and from the oblique lateral ridge and upper and lower borders 

 of the thyroid cartilage, and curves backwards, expanding as it proceeds, 

 and unites with its fellow in the middle line behind the jiharynx. The 

 direction of the inferior fibres is horizontal, concealing mid over- 

 lapping the commencement of the oesophagus ; the rest" ascend with 

 increasing degrees of obliquity, and cover the lower part of the middle 

 constrictor. 



Beliit'wnx. — Tliis muscle lies in contact posteriorly with the cervical veitebraa 

 and the longus colli muscle ; its outer surface is related to the side of the larynx, 



