( -4° ) 



coniea, which was foniewhat I'calded by the water, and therefore 

 might eafily be taken off; and, upon comprelling the ball of the 

 eye between my hngers, I iaw in many places, a thin watery matter, 

 ilTue from the tunica cornea, and appearing on its furface, like vapour 

 or fleam, adhering to a glai's, and, when the preflure was continued, the 

 watery particles, which ftood on the furface, in the form of minute 

 drops, were fo much enlarged, as to run into one another. And we 

 need not wonder at this appearance, when we confider, that the tu- 

 nica cornea is compoled of nothing but particles, like llrcaks or fibrous 

 parts with their ramifications, and all of them very thin and flender, 

 I at one time cut the tunica cornea of an ox's eye into fuch 

 thin flices, that the thicknefs of it was feven times divided, and, in 

 each of thofe feven parts, I faw with great admiration (and more 

 diflin6lly than I had before done) the great multitudes of pellucid 

 ftreaks or fibres intermixed together, many of which I judged were 

 a kind of blood velT'els, though fo fmall and flender, that they would 

 not admit the globules of blood, which caufe its red colour, to pafs 

 through them ; and I conclude that, when we rub our eyes, thofe 

 veflisls may, by the; preflure, be fo extended, as to admit the red glo- 

 bules of blood, which, for a time, flagnating there, caufe the eyes to 

 appear red, or, what is commonly called blood-fliot. 



But, to return to the eye-lids, it is my opinion, that they never 

 can be confidered as in a {fate of refl, except when they are fliut; 

 and hence it is, that we cannot keep them fteadily open, for any 

 length of time, without applying fome external force : and, as it were, 

 to give them refl, we frequently (and involuntarily) clofe them; 

 which involuntary motion in the eye-lids, does, I doubt not, by pref- 

 fnig on the orifice of ibme minute lymphatic veflels, caufe them 

 continually to emit fmall portions of the lymph, whereby the tunica 

 cornea is continually kept moift, as has been before obferved. And 

 1 have feen perfons, in a public audience, when very attentive, clofe 

 their eyes, though fome did this more frequently than others. 



