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VISCERAL ANATOMY. 



Name the Tunics of the Eyeball. 

 They number 3, and are named as fol 

 lows: the 



Sclerotic 3 and Cornea? the exter- 

 nal and protective tunic. 

 Uveal Tract, or vascular tunic, 

 comprising the Choroid, 4 Ciliary 

 body and the Iris, 8 within which 

 is the 

 Retina?^ the innermost, nervous 



tunic. 



Name the Humors of the Eyeball. 

 They also number 3, as follows : 



Aqueous* in the anterior 2 and 



middle 9 chambers. 

 Crystalline, forming the crystal- 

 line lens. ! 5 

 Vitreous? 9 ' in the posterior chamber of the eyeball. 



THE SCLEROTIC AND CORNEA. 



Describe the Sclerotic. The Sclerotic or hard coat is the posterior five- 

 sixths of the external tunic of the eyeball, the anterior one-sixth being the 

 Cornea. Externally it is of a white color, covered anteriorly by the conjunc- 

 tival mucous membrane, posteriorly being continuous with the sheath of the 

 optic nerve. Internally its color is brown, and its surface marked by grooves 

 for the ciliary nerves. The optic nerve pierces it posteriorly , also the long and 

 short ciliary arteries, posterior ciliary veins and short ciliary nerves. In the 

 equatorial region it is pierced obliquely by the venae vorticosae, and around the 

 corneal border by the anterior ciliary arteries and veins. It is composed of 

 connective tissue with elastic fibres, intermixed with pigment cells, and cells 

 resembling the corneal corpuscles. It presents for consideration the following 

 points, viz. : 



Thickness, ^V * nc h posteriorly, -^ inch anteriorly. 



Lamina Fusca, a layer of very fine connective tissue, connecting the 



sclerotic with the outer surface of the choroid. 



Lamina Cribosa, the posterior perforated portion of the sclerotic, which 

 at this point is a thin, cribriform lamina. Its largest opening transmits 

 the arteria centralis retinae, and is named the Porus Opticus, or Optic 

 Canal. 



Sub-conjunctival Tissue, connects the conjunctiva with the outer surface 

 of the sclerotic. 



