MTSCLKS i'F THE HEAP. 



57 



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

 of the red us extern us, then runs forwards and outwards. The 

 second portion (/), which lies over this and the tendon of the m. 

 rerfii.y f\rtt-rnv.s, 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 ///. red v/.? 

 interims, 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. JI. It i- at or hulbi, Duges (Figs. 48 I, 51 /, 52 /). 



Duges, fronto-pterygoidien, n. 9. Klein, sustentator bulbi. 



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 origin of the 

 m. retractor In. Hi, and 

 the tendons of the m. 

 obliguns inferior, and the 

 m. pteryyouku* ; 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- 



Trunsverse section through the 

 skull and orbital cavities of 

 Rana etculenla. 



b Bulb of eye. 



<_ Skull cavity. 



>> Mucous membrane. 



I M. levator bulbi. 



ra Upper jaw. 



>. Membrana nictitans. 



n' Continuation of same to the 



lower eyelid, 

 p L'pper eyelid. 



d.p 



I \ 

 p. t 



M. Itvator bufbi of Rana 

 etculfnta, seen from 

 above ; the eyeball 

 which rests on it has 

 been removed. 



il.p M. depressor palpe- 

 brae inferiorU. 



I M. levator bulbi. 



n Membrana nictitans. 



/-. M. pterygoideus. 



t M. temporalis. 



