THE FROG. 115 



S. The recti muscles other than the superior 

 one ; seen on removal of the levator bulbi, 

 to converge postero-internally. The inferior 

 rectus, arising from the ventral face of the eye- 

 ball and passing obliquely backwards; the 

 external rectus, arising from its posterior face 

 and passing inwards and upwards ; the in- 

 ternal rectus, arising in front under cover of 

 the inferior oblique, and passing backwards 

 along the inner face of the eye-ball. 



. The $rd (oculomotor) nerve ; seen to break up, 

 immediately in front of the superior rectus, 

 for distribution to /:?. and 8. with the excep- 

 tion of the external rectus. 



. The 6th cranial nerve (n. abducens). A small 

 muscle (pterygoid} will be seen lying in the 

 posterior region of the orbit ; remove this and 

 lay bare the Gasserian ganglion (Sect. K.p. 105); 

 the 6th nerve will be found passing from the 

 outer face of the latter to the postero-ventral 

 border of the external rectus. It is very 

 short and may best be seen by gently drawing 

 the muscle forwards. 



if]. The retractor bulbi muscle; a considerable 

 mass of tissue, seen, on removing ft. and 8. 

 It surrounds the optic nerve. 



9. The tendon of the lower lid (Cf. a. .) ; shining 

 and thread-like, passing round and intimately 

 connected with the outer edge of 17. It is 

 inserted behind into the adjacent integument. 



The origins of the yd, ^th and 6th cranial nerves. 



82 



