I.] THE FROG. US 



8. 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. 



e. The yd (oculomotor) nerve ; seen to break up, 

 immediately in front of the superior rectus, 

 for distribution to /8. 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 

 laybarethe 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. 



i). The retractor bulbi muscle; a considerable 

 mass of tissue, seen, on removing /J. and 8. 

 It surrounds the optic nerve. 



B. 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. 



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



8—2 



