30 3Ir. Booth on the Cornea of the Ei/e. [Jan. 



Article V. 



On the Cornea of the Eye. By Mr. Booth. 

 (To Dr. Thomson.) 



SIR, Barnet, Nov. 20, ISIO. 



As the pages of your Annals are not generally occupied by 

 anatomical subjects, it might be supposed the following observa- 

 tions were misplaced. But as they refer to the structure and 

 functions of the eye, and a peculiar action of that organ upon 

 light ; they are so connected, perhaps, with the other more 

 immediate objects of your journal as to allow of their insertion. 



It is a well-known anatomical fact, that if a moderate degree 

 of pressure be applied to the sides of an eye after removal from 

 the socket, its axis becomes increased ; the crystalline lens is 

 thrust forward ; the cornea becomes distended by means of the 

 aqueous humour; and, at the same time, is rendered perfectly 

 opaque. This opacity is not permanent ; for the moment the 

 pressure is removed, it regains its former transparency, and this 

 effect may be continually varied as we vary the pressure. I was 

 induced to examine this phenomenon rather more minutely, from 

 having lately observed that it was not produced in very fresh 

 eyes ; and hearing it remarked that if all the layers of the 

 cornea, except the last, are removed, this effect does not take 

 place. 



I had originally considered this opacity to depend upon a 

 peculiar polarity, given by means of the pressure to the aqueous 

 humour contained in the anterior chamber of the eve, and which 

 might become more obvious a short time after death on account 

 of some change that might have taken place in the nature of the 

 fluid. This, however, could not be the case, as the opacity 

 ceases on the removal of the several layers of the cornea, 

 although an equal degree of pressure be applied. It must, there- 

 fore, evidently depend upon some change produced by the pres- 

 sure of the aqueous humour upon that membrane. The cornea 

 cannot, in this instance, be in its natural state ; and some mecha- 

 nical or morbid alteration must previously have taken place 

 before the opacity could have been produced. I removed 

 several corneie from eyes and placed them between sHps of glass ; 

 upon applying pressure, those which had been taken from recent 

 eyes suffered no change ; while the others became opaque. 

 The opacity was the same by transmitted as by reflected light. 

 This rendered it certain as to its depending upon the cornea, 

 and to some change that must have taken place in it. After 

 death, a transudation of the aqueous humour takes place through 

 the layers of the cornea, and it is to the quantity of this fluid 

 contained between the layers that the opacity of the cornea may 

 be referred. Whether the opacity depends upon pressure com- 



