MammalianEyeball Dissection
* D. Craig Gillespie, The UniversityOf British Columbia,Vancouver, 8, Canada An easy technique is explained here to study the anatomy of the eye. The author is Assistant Professor of Education.
Many teachers of biology and physics tend sclerotic layer with motor muscle attach- to avoid dissection of the mammalian eye. ments, transparent cornea, retina, iris dia- The followin.g is a simple, neat and effective phragm, lens, (which will appear snow-
method which yields "text-book" results. white), the humors (which will appear as Downloaded from http://online.ucpress.edu/abt/article-pdf/28/4/291/22342/4441327.pdf by guest on 25 September 2021 Ask your local meat-market manager to icy crystals, and if you made a "lucky" cut, obtain some cow's eyes. These can be the entrance of the optic nerve. ordered from his regular supplier, usually Leave one-half of the eye undisturbed to without cost, if the purpose is explained. thaw gradually and serve as a reference. Most of the musculature controlling the eye Dissect the other half as follows. Use a will be severed close to the eyeball. needle to slide out the aqueous humor, lens Wrap each eyeball independently in alum- and vitreous humor onto a paper towel. The inum foil. Place the foil packages separately imprint (and perhaps part) of the iris dia- in the freezing compartment of a refrigerator phragm will be found on the aqueous humor. and allow them to freeze solid. Rinse the eyeball under the tap. The irri- Prepare a small mound of putty on a flat descent nature of the retina will be obvious. board. Secure a sharp, heavy-bladed knife. Evert the eyeball and peel off the retina. A triangular-bladed chef's knife about ten The absence of retinal tissue where the optic inches long is ideal. When you are ready to nerve enters, the "blind-spot," will be noted. do the dissection, remove an eyeball from Rinse again. the freezer and without permitting it to thaw, Beneath the retina the much-branched anchor it in the mound of putty. Look for blood supply to the choroid layer will be the severed end of the optic nerve which apparent. It is not possible to distinguish will protrude from the eyeball as a whitish- the choroid from the sclerotic layer macro- yellow structure about one-eighth of an inch scopically. Note the transparency of the lens in diameter. The nerve may be obscured by as it begins to thaw. The thawed humors and fatty tissue surrounding it. Orient the eye- the lens form syrupy solutions with varying ball in the putty in such a way that you can viscosities. make a median longitudinal section through These instructions are for a macroscopic the optic nerve. (see Fig. 1.) Make only one dissection, an imaginative teacher can pro- cleaving cut by placing the point of the knife ceed from here. on the board in front of the eye and lower- ing the rear portion of the blade through the eye. _ P_l&ne_ oF cut Place each severed half of the eye on a paper towel with the cut surface upward. The cut surfaces appear very similar to popu- (tec \NIerve lar textbook diagrams. Without disturbing any of the structures -BOttll the following features can be observed;
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