296 DETAILED SYNTHESIS. 



one. The edge is bevelled, to fit the sclerotic, though 

 they are continuous, and the cornea cannot be removed 

 without section. 



768. THE CORNEA is CONSTRUCTED of sinewy fibres, 

 arranged in many layers, so as to be perfectly transpar- 

 ent, devoid of blood-vessels, but containing many cavi- 

 ties, wrought like the lacunae in the bones, that the white 

 nutriment of the blood may reach all parts. There is a 

 canal around its edge, lined, and serving as a vein. 



769. THE CORNEA is COVERED with the delicate 

 serous membrane lining the lids, which upon the eye 

 becomes very thin and transparent, its surface-cells being 

 scale-like or squainous. 



770. THE CORNEA is LINED with an exquisitely deli- 

 cate serous membrane, that also covers the front surface 

 of the iris, or colored part of the eye. 



771. BACK OP THE CORNEA is a space lined with 

 serous membrane, just described, divided in two cham- 

 bers, the anterior, 9, and posterior, 10, by a partial mus- 

 cular partition, 6, surrounding an opening, 7, the pupil. 

 Both chambers in common are filled with a fluid, the aque- 

 ous (watery) humor, that is the second medium of the eye. 



772. THE IRIS is the colored part of the eye, with a 

 round opening in its centre through which light passes. 

 It corresponds to the choroid, as the cornea does to 

 the sclerotic, and the covering of the back part of it is 

 filled with dark pigment-cells, which give color to the 

 iris, according to their own number and the transpar- 

 ency of that portion of the iris in front of them. 



773. THE IRIS is CONSTRUCTED of muscular fibres, 

 some forming rings around the pupil, and, by contract- 

 ing, lessening it, and some radiating from the rings, 

 and, by contracting, enlarging the pupil. The muscles 

 and their action can be seen by watching the eye as a 

 light is brought near it and removed. 



T68. How ? 769. How ts ? 770. How Is ? 771. What is - ? Til. What 

 _v 773. HOW is ? 



