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those of the head, which has been already mentioned. 

 When the Ternporalis is removed, the Pterygoideus Ex- 

 ternus at its upper part is plainly to be seen through the 

 orbital foramen. This is brought about by the fact that 

 the muscle extends forward, from its insertion to its ori- 

 gin, under the Temporalis. 



The Pterygoideus Externus arises from a ridge on the 

 orbital' foramen, just posterior to the orbit of the eye, 

 and beneath the Temporalis. It is inserted into the ante- 

 rior part of that portion of the coudyle, where a little 

 projection is formed for that purpose, and also the whole 

 internal surface of the condyle of the jaw. This latter 

 part of the insertion is muscular, while the former is ten- 

 dinous. The origin throughout is by muscular fibers. 



M. Pterygoideus Interims. 



The Pterygoideus Internus is of a quadrate form, and 

 shorter than the Pterygoideus Exteruus. It has both 

 origin and insertion by muscular fibers. It arises in 

 advance of the origin of the Pterygoideus Externus, from 

 the walls of the skull. It is inserted into the inner side 

 of the lower maxillary bone, opposite the insertion of the 

 Masseter, extending from the angle of the jaw, to the 

 point directly under the coronoid process. 



M. Digastricus. 



The homologue of the Digastricus is very well shown 

 on a superficial dissection. It arises from the temporal 

 bone, directly in front of the opening of the meatus audi- 

 torius externus, on the under side of the skull. Its ori- 

 gin is by muscular fibres. From its origin it extends to 

 its insertion on the posterior aspect of the angle of the 

 jaw, posterior to the ridge, upon which the Masseter finds 



