. XX. STRUCTURE OF THE HUMAN EYE. 



363 



verge upon the retina. Such is the construction of the eye 

 of man, and of all the higher animals. 



Structure of the Human Eye.- Let us now describe the 

 form of the eye, and of the parts composing it. This organ 

 is contained in a cavity called the orbit. Its form which is, 

 almost spherical, is preserved by an exterior coat formed of 

 a fibrous dense membrane, which, at its posterior part, is 

 opaque, and is called the sclerotic coat, or the opaque cornea; 

 but at its anterior part is transparent, has an augmented 

 curvature, and takes the name of the transparent cornea. 



In the circle formed by the junction of the transparent 

 with the opaque cornea, is extended and fixed an opaque 



Fig. 31. 



A LONGITUDINAL SECTION OF THE GLOBE OF THE EYE. 



1. The Sclerotic Coat. 



2. The Cornea. 



3. The Choroid Coat. 



4. The Ciliary Ligament. 



5. The Ciliary Processes. 



6. The Iris. 



7. The Pupil. 



8. The Retina. 



9. The Canal of Petit, which encircles 

 the Lens. 



10. The Anterior Chamber of the Eye, 

 containing the Aqueous Humour. 



11. The Posterior Chamber. 



12. The Lens enclosed in its proper 

 Capsule. 



13. The Vitreous Humour enclosed in 

 the Hyaloid Membrane. 



14. A Tabular Sheath of the Hyaloid 

 Membrane. 



15. The Neurilema of the Optic Nerve. 



16. The Arteria Centraiis Retina;. 



membrane called the iris, which gives the colour to the 

 eye, and is composed of muscular fibres, one portion of 



