344 



HUMAN ANATOMY. 



It presents the following: 



Diameters. Antero-posterior, in the adult, .950 inch; 

 transverse, .925; vertical, .915; oblique, .943. 



Anterior and posterior poles are the geometric centres of the 

 cornea and fundus respectively. 



Optic axis is a straight line passing through the cornea and 

 posterior pole of the eye. 



Line of vision, or visual axis, is an imaginary line which 

 connects the point of fixation with the fovea centralis, through 

 the nodal point, usually to the outer side of the centre of the 

 pupil. It forms with the optic axis as it cuts the cornea, the 

 visual angle an angle of from 3 to 7. 



15 



Antero-posterior section of Eyeball. 1, optic nerve; 2, sclera; 3, 

 cornea; 4, spaces of Fontana; 5, choroid; 6, ciliary muscle; 7, ciliary 



Srocesses; 8, iris; 9, retina; 10, Jacob's membrane; 11, anterior cham- 

 er; 12, posterior chamber; 13, pupillary area; 14, aqueous humor; 

 15, hyaloid membrane; 16, canal of Stilling; 17, canal of Petit; 18, 

 vitreous humor; 19, capsule of the lens; 20, fluid of Morgagni; 21, 

 lens. (Leveille.) (Ball.) 



Nodal point is an imaginary point the centre of curvature 

 of the refracting media where all the luminous rays pass with- 

 out deviation. 



Equatorial plane, an imaginary plane passing through the 

 centre of the eyeball at right angles to the optic axis, dividing 

 the globe into two hemispheres the anterior and posterior. 



Equator is the line upon the surface of the globe where the 

 equatorial plane cuts it. 



Meridional planes are imaginary antero-posterior planes co- 

 inciding with the axis. 



