414 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



2. Aqueous humor. 



3. Lens. 



4. Vitreous humor. 



TUNICA EXTERNA. 



i . The sclera is a dense connective-tissue covering 

 of the eye that terminates anteriorly in the cornea. 

 It is of interest to note that, in birds of prey, horny 

 plates develop in the sclera for the better protection 



Canal of Schlemm. 



Iris. 



Cornea. 



Aqueous 

 humor. 



Lash. 



Iris. 



Tunica exierna. 



Blind 

 spot. 



Optic 



nerve. 



Ciliary body. Ora serrata. 



Fig. 286. Diagram of the eye. 



of the eye. Posteriorly the sclera is perforated by 

 the entrance of the optic nerve. Connective-tissue 

 fibers, known as the lamina cribrosa, pass across this 

 point and interlace the optic fibers, while others 

 sweep backward along the optic nerve as its external 

 envelope. 



The sclera consists of interlacing bundles of con< 



