382 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



the cornea consists only of the conjunctival epithelium. The 

 line of reflection from the lid on to the eyeball is called the 

 fornix conjunctive. 



Near the inner canthus there is also a collection of follicles 

 constituting the caruncula lacrymalis, and external to this is 

 the plica semilunaris. 



The lacrymal apparatus includes the gland, the two canals, 

 the sac, and the nasal duct. 



The gland is about the size and shape of a small almond, 

 and lies in a depression in the orbital plate of the frontal bone 

 just inside the external angular process. Above it is attached 

 to the periosteum, and below it rests on the eyeball and the 

 upper and outer recti. In front it is closely connected to the 

 upper lid and is covered by conjunctiva. Its ducts, ten or 

 more in number, run beneath the conjunctiva and open sepa- 

 rately at the outer part of the fornix. 



The lacrymal canals commence by small orifices, the puncta, 

 on the margin of each lid, and empty close together into the 

 sac. The upper and longer ascends at first, then runs down- 

 ward and inward; the lower ones downward, then inward. 



The lacrymal sac is the upper dilated part of the nasal 'duct, 

 and lies in a depression formed by the lacrymal and superior 

 maxillary bones; it is invested by an aponeurosis derived from 

 the tendo oculi, and is crossed by the tensor tarsi. 



The nasal duct is contained in a canal formed by the superior 

 maxilla, lacrymal and inferior turbinated bones, and runs 

 from the lacrymal sac to the inferior meatus. It is lined with 

 a mucous membrane continuous with the conjunctiva, is 

 narrowest in the middle, and at its lower expanded orifice 

 is the valve of Hasner. Its direction is downward, backward, 

 and outward. Its epithelium is ciliated. 



The eyeball consists of three coats enclosing the refractive 

 media or humors. They are the sclerotic and cornea outside, 

 the retina internally, and the choroid between them. 



The sclerotic coat is a dense fibrous membrane, white and 

 smooth externally, excepting where it receives the insertion 

 of the recti and obliqui. Internally it is brown, grooved by 

 the ciliary nerves, and united by a connective tissue, the 

 lamina fusca, to the choroid beneath. It covers the posterior 

 five-sixths of the eyeball. Behind it receives the optic nerve 

 at a point just internal to the centre, the fibrous sheath of 



