SCLEROTIC COAT. 



791 



FIBROUS COAT OF THE EYEBALL. The outer casing of the eye Fibrous 

 consists of an opaque hinder part called sclerotic, and of an anterior coat - 

 transparent portion, the cornea. 



The SCLEROTIC is the firm, whitish, opaque portion of the outer Sclerotic 

 oat of the i-yeball, which supports the more delicate structures part * 

 within. 



Dissection. To examine the inner and outer surfaces of this layer, Dissection 

 it will be necessary to cut circularly with scissors through the 



FIG. 288. DIAGRAM OF A HORIZONTAL SECTION OF THE EYEBALL. 



a. Sclerotic coat. 



b. Choroid. 



c. Ketina. continuous with the 

 optic nerve behind, with a dark 

 layer outside it. 



d. Cornea. 



e. Ciliary muscle. 

 /. Iris. 



f. Lens. 

 . Vitreous body. 

 i. Posterior chamber of the aqueous. 



I. Optic nerve. 



m. Circular fibres of the ciliary 

 muscle. 



II. Hyaloid membrane, 

 o. Canal of Petit. 



r. Canal of Schlemm. 



s. Ciliary process. 



t. Suspensory ligament of lens. 

 The dotted line through the centre is 

 the longitudinal axis of the ball. 



cornea close to the sclerotic, and to remove the cornea from the 

 front of the eyeball ; on piercing the cornea the aqueous fluid 

 escapes from the containing chamber. The other structures may 

 be then abstracted from the interior of the sclerotic covering, and 

 may be set aside in water with the cornea for subsequent use. 



The sclerotic tunic of the eye (fig. 288, a) extends from the Extent of 

 entrance of the optic nerve to the margin of the cornea, forming sc 

 above five-sixths of the ball. 



At its back, and a little to the inner side of the centre (one-tenth apertures 



behind, 



