The Head and Neck. 



249 



inserted on the medial portion of the eyeball around the 

 optic nerve. It consists of four distinct parts. 



(f) The Harderian gland (gl. Harderiana) is a large compact 

 gland lying in the anterior portion of the orbit. It is com- 

 posed of two portions, one of which is greyish red, the other 

 white. The duct opens on the inner surface of che third 

 eyelid. 



(g) The lacrimal gland (gl. lacrimalis) is a much smaller, also 

 darker, structure lying close to the skull in the temporal 

 angle of the orbit. It communicates by several fine ducts 

 with the inner surface of the upper eyelid. 



The infraorbital gland (gl. 

 infraorbitalis) is a diffuse white 

 or yellowish gland lying in the 

 anteroventral angle of the orbit 

 immediately medial to the zygo- 

 matic arch. The gland is one 

 of the salivary series, its duct 

 passing downward and opening 

 through the mucous membrane 

 of the cheek into the cavity of 

 the mouth. 



To examine the structure 

 of the eye, the muscles of 

 the eyeball should be divid- 

 ed at their insertions, and 

 the whole structure re- 

 moved. The second cra- 

 nial or optic nerve (n. 



opticus) is divided; also the ophthalmic artery, a small branch 

 of the internal carotid which accompanies the nerve outward from 

 the optic foramen to the eyeball. 



The eye may be divided by a circular incision into medial 

 and lateral hemispheres, the lateral hemisphere, containing the lens, 

 being again divided vertically. The parts should be examined 

 under water. The chief structures (Fig. 80) comprise: 



(a) The fibrous tunic (tunica fibrosa oculi), the strong peri- 

 pheral coat enclosing the whole structure. It is divisible 

 into a medial portion, the sclera, or sclerotic coat, a thick 



p>- 



Fig. 80. Diagram of the parts of the eye in 

 vertical section: c.a., anterior chamber; c.c, 

 ciliary body; ch., chorioidea; co., cornea; c.p., 

 posterior chamber; c.r., ciliary portion of the 

 retina; c.v., vitreous body; d.h., Harderian duct; 

 d.l., position of the lacrimal ducts; d.n., nasola- 

 crimal duct; i., iris; I., lens; n.o., optic nerve; 

 o.r., optic portion of the retina; p.i., lower 

 eytlid; p.s., upper eyelid; p.t., third eyelid; 

 r.b., retractor oculi; r.i.. rectus inferior; r.s.. 

 rectus superior; sc, sclera; z., suspensory 

 zonular fibres of the lens. 



