262 Mammalia, 



the scissors tlirougli the Cornea, all round, at its junction 

 with the Sclerotic, and remove the Cornea from the front of the 

 eyeball. On piercing the Cornea the Aqueous humor, above 

 mentioned, will escape from the chamber of which the Cornea 

 forms the outer wall. 



The Aqueous humor differs little from water in its physical 

 characters : but it contains a small quantity of some solid 

 matter, chiefly chloride of sodium (in the human subject), dis- 

 solved in it. 



The Cornea is readily separable into two layers, one fibrous, 

 and the other firm but structureless, retaining its transparency 

 for a long time ; of these, the former, made up of a series of 

 fine superposed layers, and lined posteriorly by a very thin 

 structureless membrane, known as the membrane of Demours, 

 is the Cornea proper ; the latter, consisting of a basement 

 layer (anterior elastic lamina) covered by Epithelium, is the 

 Corneal Conjunctiva. The Epithelium in front of the 

 * anterior elastic lamina ' demands special notice ; for in the 

 Horse, the Ox, and the Sheep, it has a much more remarkable 

 appearance than in Man, and one not to be accounted for by 

 the ordinarily presumed mode of growth of stratified epithelia ; 

 for the deepest cells are greatly elongated and larger than 

 those which are immediately superimposed, and have precisely 

 the appearance of true columnar epithelium, the flat ends 

 resting on the subjacent elastic lamina, and the pointed ex- 

 tremities directed forwards.* 



The Chamber of the Aqueous Humor^ which has been thus 

 opened into, was formerly said to be partially divided into 

 two chambers which communicated through the Pupil ; but 

 it has now been ascertained that in Man the pupillary margin 

 and part of the posterior surface of the Iris are in contact 

 with the Capsule of the Lens, thereby closing the chamber 



* Quain and Sharpey, ii. 715 (Ed. 7). 



