ORGANS OF THE SENSES. 505 



VISION. 

 Structure of the Globe of the Eye. 



The structure of the several appendages of the globe of 

 the eye : as the eye-lids, with their lashes, and Meibomian 

 glands, the caruncula lacrymalis, the lachrymal gland, muscles, 

 &c., have already been fully described in previous sections of 

 this work ; we have now to enter upon the description of the 

 numerous parts which compose the essential portion of the 

 organ of vision, the globe of the eye ; each of these may be 

 examined in much the same order in which they would 

 naturally present themselves to the notice of an ordinary 

 dissector, and which would be somewhat as follows. Schle- 

 rotic and cornea ; choroid, ciliary processes, and iris ; retina ; 

 crystalline lens ; hyaloid membrane, &c. 



Schlerotic. 



The schlerotic is composed, to a great extent, of white 

 fibrous tissue, intermixed with a small proportion of a nu- 

 cleated form of elastic tissue. 



These tissues are disposed in a laminated manner, the fibres 

 of one layer crossing those of another more or less at right 

 angles ; an arrangement evidently designed to render this the 

 protecting tunic of the eye more firm and unyielding. The 

 inner surface of the schlerotic is rough, and connected with 

 the choroid by the lamina fusca of that membrane, to be 

 described hereafter. 



The nutrition of the schlerotic is provided for by small 

 vessels, which ramify on its outer surface, and which are 

 sparingly continued into its substance. 



Anteriorly, the schlerotic is strengthened by the tendinous 

 expansion of the four recti muscles, known as the tunica 

 albuginea, or white of the eye. 



