VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 83 



it resembles the epidermis. This opinion is founded on its want of sensibility, and 

 having no vessels whieh carry red blood; the appearance it puts on when preserved in 

 spirits, which is exactly similar to the nails at their roots, probably confirmed this 

 supposition. As the cuticle is devoid of life, it is only under the influence of dis- 

 ease during its growth; once formed, it continues unchanged. The cornea, were 

 it of the same nature, would be equally incapable of taking on new actions from 

 disease, or any other cause; but we find, on the contrary, that it undergoes many 

 changes, which exactly correspond with those which the living parts of an animal 

 body go through when under the influence of disease; from which I am induced 

 to consider it alive; and I find that many of the present teachers of anatomy are 

 of the same opinion. 



To prove that the cornea has life, it is necessary, as a previous step, to show, 

 that being supplied with vessels which carry red blood, and having sensibility, are 

 not essential to the possession of the living principle; for this purpose all that is 

 required, is to demonstrate that there are living parts which have neither the one 

 nor the other. Tendons and ligaments in a natural state are instances of this 

 kind. That these parts are not supplied with red blood, is obvious to the eye of a 

 common observer; no illustration will therefore be required to substantiate that 

 proof. That they are not endowed with sensibility was, I believe, first taught by 

 the late Dr. William Hunter,* who published the following account of it.-f- In a 

 case where the last joint of the ring-finger had been torn off, half an inch of the 

 tendon of the flexor muscle projected beyond the stump; this it was thought right 

 to remove; and to ascertain whether it was possessed of sensibility, the following 

 experiment was made: a piece of cord, the thickness of the tendon, was passed 

 round the wrist and along the side of the finger, so as to project even with the end 

 of the tendon; the man was told to turn away his head, and tell which of the 1 

 were cut through ; the tendon was divided, and the man declared it was the string, 

 not having felt the smallest degree of pain. 



This proof is satisfactory ; but that the cornea is possessed of life, by no means 

 rests on any negative proofs; which I shall now endeavour to explain. The cornea 

 in its structure is made up of membranous laminae. One of these appears to be a 

 portion of the tunica conjunctiva ; but it is either so extremely thin, or so inti- 

 mately connected with the lamina next to it, as not to admit of more than a very 

 partial separation from it; another lamina, as I have shown in a former lecture, is a 

 continuation of the tendons of the 4 straight muscles; but as both of these laminae 

 have the same properties as the other parts of the cornea, and are not to be distin- 

 guished from them, they must be considered in every respect as a part of it. The 

 tunica conjunctiva and tendons, a continuation of which forms these anterior 

 laminae of the cornea, are allowed to be living parts, and the portions that make 



* This doctrine was first taught by Dr. Hunter, in the year l74fj. Haller made experiments proving 

 the same thing in 1750. t Medical Observ. and Inquir. Vol. 4, p 343. — Orig. 



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