244 Mammalia. 



most externally, the Lachrymal and Supra-orbital branches of 

 the Ophthalmic division of the Fifth nerve. 



The orbital membrane may now be further reflected on the 

 outer side, and the fat carefully removed ; by which means 

 the origin of the inferior rectus will be disclosed, adjoining 

 that of the external rectus ; and between the edges of these two 

 muscles will be seen a stoutish nerve running forwards, and 

 a thin nerve running backwards, both meeting at a spot about 

 half an inch from the origin of the muscles. Of these two 

 nerve- cords, that running forwards is the continuation of 

 the Third nerve, and that running backwards is a factor from 

 the Fifth nerve, en route to the CiKary ganglion. 



The Student should now carefully separate the contiguous 

 margins of the superior and external recti muscles; turn 

 each away from the other, and remove the fat. 



The further course of the Nasal branch of the Ophthalmic 

 division of the Fifth wer^^e will then be made out, tending inwards 

 across the stalk of the Choanoid or Suspensorius muscle, and 

 then across the origin of another muscle arising close to it, 

 vis:., the internal rectus. Arrived at this point, the nerve 

 will be found to bifurcate, one branch, after gaining the 

 anterior edge of the superior oblique muscle (between which 

 and the internal rectus it has just passed,) re-enters the cranial 

 cavity through a foramen in the orbital plate of the frontal 

 bone, to pass through the cribriform plates of the Ethmoid 

 bone, and be distributed on the walls of the nasal fossae : the 

 other branch continuing further forwards to the margin of the 

 orbit, to be distributed to the lachrymal sac, eyelids, and side 

 of nose. 



If now the stalk, or origin of the suspensorius, be gently 

 pushed on one side away from the superior rectus, the large 

 white Optic nerve will be brought into view, and a little more 

 of the course of tlm Third nerve, vi^., where it dips under the 

 pedicle of the Suspensorius in company with the Optic nerve. 



