390 



ANATOMY IN A NUTSHELL. 



above the other orbital nerves. In this position it communicates with the 

 ophthalmic division of the fifth and with the cavernous plexus. Before enter- 

 ing the sphenoidal fissure it divides into two branches, a superior and an in- 

 ferior one, with the nasal branch of the fifth nerve between them. (Plate 

 ( CXXIV). All the structures on the Lower border of the sphenoidal fissure are be- 

 tween tlif two heads of the External rectus muscle. The superior branch is the 

 smaller, h passes forward over the optic nerve and supplies the Levator 

 palpebrae and Superior rectus muscles. The inferior branch supplies three 

 muscles; the division which goes to the Internal rectus passes beneath the optic 

 nerve; the second division passes to the Inferior rectus, and the third or lower 

 division passes to the Inferior oblique between the External rectus and the In- 

 ferior rectus. This division to the Inferior oblique sendsa motor branch to the In- 

 ferior rectus. The branches of the third nerve enter their muscles on the orbital 

 surface except the branch to the Inferior oblique which enters on the posterior 

 1 inn ler. This third nerve may supply the anterior belly of the Occipito-frontalis, 



PLATE CCV. 



DUCTS OF LACHRYMAL GLAND. 



LACHRYAMAL SAC 



CARUNCLE 



NASAL .DUCT 



Nasal Duct, Conjunctiva, and Lachrymal Gland. 



the Corrugator supercilii, and the Orbicularis palpebrarum. These muscles 

 are generally supplied by the seventh, but they have escaped paralyses in lesions 

 of the nuclei of the seventh nerve. From the nucleus of the third nerve some 

 fibers which descend in the posterior longitudinal bundle join the facial nerve 

 ju.-t before it leaves the pons; these fibers supply the three muscles above men- 

 tinned. Paralyses of the third nerve may be only in part as any fibers to one 

 muscle or it may be the whole nerve. When the whole nerve is paralyzed the 

 following result : (1 ) Prominence of the eye-ball because most of the mus- 

 cles are relaxed. (2) Extern vl strabismus, the eye-ball being drawn outward 

 because the External rectus which is supplied by the sixth is not paralyzed. 

 (3) Ptosis because the Levator palpebrae is paralyzed. (4) Loss of accommoda- 

 tion because the [nternal rectus, the ciliary muscle, and the sphincter pupillse 

 are paralyzed. (5) Dilatation of the pupil because the sphincter fibers of 

 the iris are paralyzed. 



