260 Mammalia. 



As before noted (p. 228), the bones follow one anotber tbns : 

 stylo-byal, epi-byal, cerato-byal, and thyro-byal ; the basi- 

 byal forming an angular prominence between the thyro- and 

 cerato-hyals. 



Y. D ISSECTION 



OF THE 



EYE OF THE OX.* 



External. To see the general form of the ball of the Eye, 

 and the outer surface of the external coat, the attachment of 

 the different muscles should be taken away, and the fat re- 

 moved which surrounds the white chord of the optic nerve : 

 by this means we shall be enabled to see from back to front 

 the following structures : posteriorly, is the Optic nerve, 

 attached to the back of the globe but considerably to one side 

 of its axis ; next, the Sclerotic ((TKXrjpogf hard) coat, i.e. the 

 opaque posterior five- sixths of the ball ; and, anteriorly, the 

 Cornea {corneus, horny), i.e. the smaller transparent sixth part 

 of the ball. The outer surface of the Sclerotic coat is smooth 

 except where the muscles have been attached. The Cornea 

 and front portion of the Sclerotic are covered by mucous 

 membrane, called the Conjunctiva, being the reflected portion 

 of the under lining of the eyelids, much simplified in 

 character ; and where the tendons of the four Itecti expand 

 over it anteriorly, partly covered by the Conjunctiva, a thin 

 tendinous layer is seen, called the " white of the eye." The 

 Cornea is seen to be elliptical, transparent, and convex 



N.B. A general notion of the structure of the Eye may be gained by pur- 

 suing the following shorter method of dissection, viz. 



After all the muscles have been removed, pin the Eye to a loaded cork ; then 

 place the cork in a deep pie-dish, and fill the dish with water so as to cover the 

 Eye, and proceed to expose the coats of the Eye by a series of windows, thus : 



1. Kemove about half of the Sclerotic and Cornea : 2. Remove a smaller por- 

 tion of Choroid and Ciliary processes : and 3. Remove a small portion of the 

 Retina. 



By this means all the coats are seen at the same time, and in situ. C.Robbrtson. 



