VERTEBRATE EYE 1 



1. Place a dissecting microscope on its side in front of you and turn the 

 mirror in such a position that you can examine your own eye. Make a 

 drawing, showing (a) the eyelids ; (6) the white of the eye (sclerotic 

 coat) which in front forms (c) the transparent cornea ; (d) the under- 

 lying colored portion (iris) with (e) a circular, central opening (pupil). 



2. Examine the eye of a Pig or Sheep, which has been removed from 

 its orbit. Note : (a) the shape ; (6) the character of the outer, protective 

 covering (sclerotic coat) ; (c) the attachment of the muscles ; and 

 (rf) the optic nerve. 



3. For details of the internal anatomy, examine an eye which has been 

 cut in half and find the following structures : (a) the sclerotic coat, a 

 comparatively thick layer of connective tissue, which, in the front of the 

 eye, forms (6) the transparent cornea; (c) the choroid coat, a thin, 

 deeply pigmented, vascular layer which, in the front of the eye, forms 

 (d) the colored iris, in the center of which is (e) the circular opening 

 (pupil) ; (/) the transparent lens, which lies just posterior to the iris ; 

 and (g) the sensory layer, or retina, which is directly continuous with 

 (h) the optic nerve, running from the posterior part of the eye to the 

 brain. 



4. Note the following chambers of the eye : (a) the anterior chamber, 

 situated between the cornea and iris ; (b) the small posterior chamber, 

 situated betwen the iris and lens and communicating with the anterior 

 chamber through the pupil ; and (c) the large vitreous chamber poste- 

 rior to the lens, in which the retina lies. The vitreous chamber is filled 

 with a transparent, jelly-like material (vitreous humor). The two 

 chambers in front contain a more fluid substance (aqueous humor). 



5. Make a drawing, about three inches in diameter, showing the struc- 

 tures as observed. 



i B. pp. 215-220. 



351 



