Fig. 42—Showing method of cutting through the crystalline lens.
To cut the eye in two, use a safety-razor blade; never a scalpel. The latter is too thick, too dull, and too clumsy a tool. Begin by cutting through the optic nerve; dividing it as nearly as possible into halves. ([Fig. 41].) Continue cutting through the sclerotic and all underlying tissues, stopping at the corneo-scleral junction, but do not, during this procedure, even touch the lens. After the eye has been thus partly separated into, as nearly as possible, two equal parts, lay it down upon the cornea, and, holding the razor blade in the forefingers and thumbs of both hands, cut the lens in two by forcing the blade down through it. ([Fig. 42].) Partly open the cut eye to allow one jaw of the large scissors to enter, turn the eye over so the cornea will rest on that jaw, and then cut through the cornea. ([Fig. 43].)
Fig. 43—Showing method of cutting through the cornea and completing the two sagittal sections.
The two specimens may be kept indefinitely by placing them in a 3 per cent. formaldehyde solution. It will be well to remove the lens from one of the specimens, because it will give better opportunity to see the anatomical relationships. Also, these specimens should be mounted, one above the other, between two pieces of glass, before placing them in the receptacle that is to hold them.
Much can be studied in such specimens. Moreover, they present to view the various parts of the organ of vision in such an impressive way, that one does not soon forget the wonderful appearance of the construction of this, Nature’s perfect camera. ([Fig. 44].)
Fig. 44—Sagittal section enlarged.
If another eye is cut into two parts, additional interesting specimens may be procured; for instance, one showing the presence of the second coat only, the retina having been torn out. Another good specimen may be made by removing all of the inner tissues, and leaving only the sclerotic and cornea. This specimen will show that the first coat is almost entirely a coat which affords strength and protection to the parts that lie within.