MUSCLES OF THE HEAD. 



57 



middle line, is broad and fleshy, and covers, from below, the tendon 

 of the rectus externm, then rvms forwards and outwards. The 

 second portion [r), which lies over this and the tendon of the m. 

 rectus extermts, has also a broad and fleshy origin, but runs more 

 directly forwards, slightly crossing- the preceding. The third 

 portion arises above the two others by a strong thin tendon from 

 the parasphenoid : it runs almost in the direction of the iii. rectus 

 hiternns, but more directly forwards. The first two portions 

 pass more to the upper surface of the eyeball, the third more 

 to the under surface ; consequently the whole muscle forms a 

 sheath surrounding the eyeball. The fibres to the upper surface 

 of the eyeball are inserted somewhat in front of the equator of 

 the eyeball, those to the under surface somewhat behind it. 



8. M. levator hulbi, Dugès (Figs. 48 /, 51 I, 52 I). 



Dugès, fronto-pterygoidien, n. 9. — Klein, sustentator balbi. 



There is no bony floor to the orbital cavity, and the oral and orbital 

 cavities are only separated by soft tissues; these are : — the mucous 

 membrane of the mouth, 

 a thin fascia, and above 

 this the muscle under 

 consideration. The fibres 

 of this muscle run from 

 before and from the inner 

 side obliquely backwards 

 and outwards, below all 

 the remaining muscles of 

 the eye, with the excep- 

 tion of the orig'in of the 

 m. retractor hullji, and 

 the tendons of the m. 

 obliquus inferior, and the 

 m. pterygoideus ; they 

 arise on the inner side 

 from the upper and outer 

 border of the fronto- 

 parietal bone (Fig. 51), 

 also from the transverse portion of the parasphenoid and ptery- 

 goid bones, anteriorly from the sphenethmoid and palatine bones ; 

 they run first downwards, then, in the direction indicated, under- 



I'lansverse section tlirough the 

 skull and orbital cavities of 

 Rana escuknfa. 



b Bulb of eye. 



c SkuU cavity. 



II Mucous membrane. 



I M. levator bulbi. 



m Upper jaw. 



H Membrana nictitan.s. 



n' Continuation of same to tlie 



lower eyelid. 

 p Upper eyelid. 



M. levator bidbi of Rana 

 esculetita, seen from 

 above ; the eyeball 

 which rests on it h;iji 

 been removed. 



d.p M. depressor palpe- 

 brae inferioris. 



I M. levator bulbi. 



n Membrana nictitans. 



p. M. pterygoideus. 



t M. temporalis. 



