20 THE MYOLOGY OF THE RAVEX. 



a double tendinous slip. One of these is inserted into a 

 little spine-like process on the upper side of the shaft 

 of the corresponding pterygoid, close to its quadratal 

 articular end. The other is inserted into the quadrate 

 itself, close to the pterygoidal articulation, and to its 

 outer side. 



When these muscles contract, they pull forward 

 the quadrates and pterygoids, which latter, in push- 

 ing against the palatines, tend to raise the superior 

 mandible. 



18. The pterygoideus internus forms, with the aid of 

 its fellow, the great muscular mass which is found at the 

 roof of the mouth. It has a very extensive origin. On 

 the upper side of the palatine the fibres arise over nearly 

 the entire surface, at first fleshy, to become tendinous 

 along the hinder margin of the bone. Similarly, on the 

 inferior aspect they fill the fossa there found. As the 

 fasciculi of this muscular mass pass backwards and out- 

 wards, they are augmented by others, which find their 

 origin upon the distal head and shaft of the corre- 

 sponding pterygoid and the sphenoidal rostrum for 

 some distance behind it. The fibres converge moder- 

 ately, to make an extensive tendinous insertion upon 

 the antero-internal aspect of the articular end of the 

 mandible. Mesially, they are carried out to the ex- 

 tremity of the inturned tip, w r here the tendon is very 

 strong ; while beyond they encroach slightly upon the 

 ramus, where the insertion is more of a fleshy character 

 (Figs. 5 and 6). 



19. The pterygoideus externus is an exceedingly 

 neat and well-defined muscle. It arises from the outer 

 aspect of the extremity of the orbital process of the 

 quadrate. The fibres form a roundish bundle, and 

 slightly diverge as they pass forwards, downwards, and 



