MUSCLES OF THE NECK. 371 



Pterygoideus Internus,. 



The Internal Pterygoid muscle arises by tendinous and fleshy 

 fibres from the internal pterygoid process of the sphenoid bone, 

 along the outer margin of the Eustachian tube, and from the 

 greater part of the pterygoid fossa. Passing downwards and 

 backwards, it is inserted tendinous and fleshy into the internal 

 face of the angle of the lower jaw. 



When the muscles of the opposite sides act, they close the 

 jaw. 



SECT. H. MUSCLES OF THE NECK. 



Of the Fascia Superficialis CoIlL 



Between the skin of the neck and its superficial muscles, 

 may be observed a layer of compact cellular substance, the 

 consistence of which is more strongly marked in some subjects 

 than in others. It is the continuation of the same membrane 

 which is spread upon the external abdominal muscles, and is 

 called there the Fascia Superficialis Abdominis. Passing from 

 the abdomen over the thorax, it adheres to the clavicles and 

 sternum, but not very strongly; it then goes from them over the 

 neck to the face, being slightly fastened to the base of the lower 

 jaw in advance of the masseter muscle. 



It is spread over the submaxillary and parotid glands, is in 

 many subjects strongly marked there by its fibrous character ; 

 and sends down partitions between their lobules, as well as be- 

 tween the muscles and their fasciculi; thereby forming sheaths 

 for the same. By these partitions it communicates with the 

 fascia profunda colli. Above, it is fixed to the mastoid process, 

 to the meatus auditorius externus, and to the zygoma. Just 

 above the latter it adheres to the fascia temporalis, and a thin 

 layer of fat intervenes between them. This fascia is more 

 strongly characterized about the parotid gland and lower jaw 

 than elsewhere. It is remarkably distinct in the fretus at full 

 time, the sheaths, which it forms for the muscles, being then 

 very clear of adipose matter, and semi-diaphanous. 



