88 DISSECTION OF THE PTERYGOID REGION- 



minus of the jaw, ami the masseteric branches of nerve and artery enter- 

 ing it ut the under surface. 



Action. It raises the lower jaw with the internal pterygoid in the mas- 

 tication of the food. 



Dissection. To lay bare the temporal muscle to its insertion, the follow- 

 ing dissection may be made : The temporal fascia is to be detached from 

 the upper border of the zygomatic arch, and to be removed from the sur- 

 face of the muscle. Next, the arch of the zygoma is to be sawn through 

 in front and behind, so as to include all its length ; and is to be thrown 

 down (without being cut off) with the masseter muscle still attached to it, 

 by separating the fibres of that muscle from the ramus of the jaw. In 

 detaching the masseter muscle, its nerve and artery, which pass through 

 the sigmoid notch, will be found. 



The surface of the temporal muscle may be then cleaned ; and to ex- 

 pose its insertion and deep origin, let the coronoid process be sawn off by 

 a cut passing from the centre of the sigmoid notch nearly to the last molar 

 tooth, so as to include the whole insertion of the muscle. Before sawing 

 the bone let the student find and separate from the muscle the buccal ves- 

 sels and nerve issuing from beneath it. Lastly, the coronoid process should 

 be raised and the fat removed, in order that the lower fibres of the tem- 

 poral muscle, and their contiguity to the external pterygoid close below 

 them, may be observed. 



The temporal muscle (fig. 18, *) takes its origin from the whole of the 

 temporal fossa (p. 20), reaching up to the semicircular line on the side of the 

 skull, and downwards to the crest on the outer aspect of the great wing of 

 the sphenoid bone. From this extensive attachment, as well as from the 

 fascia over it, the fibres converge to a superficial tendon, which is inserted 

 into the inner surface of the coronoid process, as well as into a groove on 

 the same process which reaches from the apex to near the last molar tooth. 



Behind the posterior border of the tendon are the masseteric vessels and 

 nerve, and in front of it the buccal vessels and nerve : the last nerve per- 

 forates occasionally some of the fibres of the muscle. 



Action. All the fibres contracting the muscle will raise the mandible 

 and press it forcibly against the upper jaw ; but the hinder fibres may re- 

 tract the lower jaw after it has been moved forwards by the external ptery- 

 goid. 



Dissection. For the display of the pterygoid muscles (fig. 18), it will 

 be necessary to remove a piece of the ramus of the jaw. But the greater 

 part of the temporal muscle is to be first detached from the subjacent bone 

 with the handle of the scalpel, and the deep temporal vessels and nerves 

 are to be sought in its fibres. 



A piece of the ramus is next to be taken away by sawing across the 

 bone close to the condyle, and again close above the dental foramen ; arid 

 to make the dental vessels and nerve in contact with its inner surface 

 secure from injury, the handle of the scalpel maybe inserted between them 

 and the bone, and carried downwards to their entrance into the foramen. 

 The masseteric artery and nerve are liable to be cut in sawing the bone; 

 should these be divided, turn them upwards for the present, and afterwards 

 tie together the ends. 



After the loose piece of bone lias been removed, and the subjacent parts 

 IVeed from much fat, tiie pterygoid muscles will appear, the external ( 2 ) 

 being directed outwards to the condylc of the jaw, and the internal ( 3 ), 

 which is parallel in direction to the masseter, being inclined to the angle 



