LESSON XXXIX 



THE SENSE ORGANS (Continued) 

 VISION 



1. Dissection of the Eye. Procure an ox eye. Having identified 

 the lids, conjunctiva, and different structures attached to the eyeball, 

 isolate the optic nerve and cut away the muscles and fatty tissue. Open 

 the anterior chamber of the eye by a transverse incision through the 

 cornea. Study the physical characteristics of the aqueous humor. 

 Remove the cornea and examine the iris and neighboring parts. By 

 exerting a gentle pressure upon the outer coat of the eyeball force the 



FIG. 107. DIAGRAM OF A HORIZONTAL SECTION THROUGH THE HUMAN EYE. 



C, Cornea; A, anterior cavity; P, posterior cavity ; L, lens; J, iris; T, conjunctival sac; 

 CL, ciliary ligament; CB, ciliary body; CM, ciliary muscle; OS, ora serrata; CS, canal of 

 Schlemm; R, retina; Ch, chore id; S, sclera; ON, optic nerve; A, retinal artery; B, blind 

 spot; Y, yellow spot; OA, optical axis; VA, visual axis; H, hyaloid canal. 



lens through the pupillary orifice. Examine the lens, noting the degree 

 of convexity of its anterior and posterior surfaces. Hold it over print. 

 Place it under water. Can it be readily seen now? Explain. Open 

 the posterior chamber widely, noting the differences in the color of the 

 fundus. Explain. Identify the optic papilla and obtain an idea re- 

 garding the location of the yellow spot. Note the characteristics of 

 the vitreous humor. Examine histologic preparations of the cornea, iris, 

 lens, and retina. 



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