THE HEAD, ANTERIOR, 57 



the head of a small pin. Is situated at the outer and upper 

 part of the optic nerve at about its middle, between the nerve 

 and the external rectus and one-fourth of an inch in front 

 of the sphenoidal fissure. 



The ganglion receives its sensory root from the nasal 

 nerve (the long root), the motor root, from the third cranial 

 nerve (the short root), and its sympathetic root from the 

 plexus on the carotid artery within the cavernous sinus. 



Eight or ten minute filaments pass forward from the gan- 

 glion the short ciliary nerves to supply the eye-ball. 



The Optic Nerve. Figs. 10, n, 12. 



The optic nerve enters the orbit through the optic fora- 

 men with the ophthalmic artery, as already described, lying 

 above and to the inside of the artery. It passes forward to 

 enter the back of the eye-ball. 



The optic nerve is the central structure passing to the 

 eye. It is surrounded by the ocular nerves, arteries, veins, 

 and muscles, and a packing of adipose tissue between them 

 all to hold them in their proper places. 



The Sixth Cranial Nerve. Figs. 10, n, 12. 



It comes into the orbital cavity through the sphenoidal 

 fissure and between the two heads of the external rectus 

 muscle, to which it is distributed. Diags. 3 and 4. 



DISSECTION. 



Complete the dissection of the eye cavity by dividing the internal and ex- 

 ternal oblique muscles and raising the eye-ball first to one side and then to 

 the other. 



The Third Cranial Nerve. Figs. 10, n, 12. Diags. 3 



and 4. 



The motor oculi enters the orbit through the inner part 

 of the sphenoidal fissure in the shape of two branches, 



