246 PRACTICAL HISTOLOGY. 



CHAPTER XX. 



THE ORGANS OF THE SENSES THE EYE. 

 THE EYELIDS, SCLEROTIC, AND CORNEA. 



THE study of the eye should be made as much as 

 possible from that of the human subject, for there 

 are slight differences in the structure of some of the 

 parts in man and animals, and, moreover, it is on 

 the whole easier to demonstrate the structures in 

 the human eye. On the other hand, there is no 

 organ which it is so absolutely essential to obtain 

 in a perfectly-fresh condition. For this and other 

 reasons it is scarcely possible to get material from 

 the post-mortem room, and the only opportunities 

 that usually present themselves occur when an eye 

 is removed on account of some injury or disease 

 which is confined to a particular part ; the other 

 intact portions may in such cases be available for 

 histological purposes. In rare instances an entire 

 healthy eye has to be removed (in operating for the 

 removal of extensive rodent ulcers of the brow and 

 face this may be necessary), and if the student should 

 be able to procure such an one, the following would 

 be perhaps the best way to deal with the excised 

 organ with the view of making the best use of it : 

 As soon after removal as possible separate the eye, 

 by an oblique cut with a very sharp knife or razor, 

 into two halves, an anterior and a posterior ; the 

 cut to start from just behind the attachment of the 

 iris anteriorly and superiorly, and pass downwards 

 and backwards towards the posterior part of the 

 organ, coming out a little below the yellow spot 

 and optic nerve. Then put the posterior part, after 



