116 



of the optic nerve over every portion of the interior 

 surface of the choroides, till it arrives at the edge 

 of the crystaUine lens. 



The cornea is formed by the first membrane, the 

 conjunctiva : it is the transparent convex substance 

 that forms, as it were, the outward case for the 

 pupil and iris. 



The anterior chamber of the eye, being the cavity 

 between the cornea and the iris, and the posterior 

 chamber, which extends from the iris inwardly to 

 a reflection of the choroides, called the uvea, are 

 both occupied by a transparent fluid named the 

 aqueous humour. 



The crystaUine lens is also a firm but transpar- 

 ent humour, of a convex form ; it is contained in a 

 very delicate membrane, called the capsula, and is 

 imbedded in the vitreous humour — a very fine 

 transparent fluid, filling the whole cavity of the 

 globe, behind the lens. 



Externally, the eye-ball and the cornea are lu- 

 bricated by the tears. 



There is some difference in the construction of 

 the human eye, and that organ in the horse ; the 

 tears have a variety in their passage into the nostril, 

 and there are seven muscles that are employed in 

 the motion of the horse's eye, whereas there are 

 only six in a man : but a minute anatomical exami- 



