12 
Mr. Home's Lecture 
If the cornea is examined at its attachment to the sclerotic 
coat and tendons of the straight muscles, it appears to be of 
exactly the same thickness with those parts, but grows thicker 
towards the centre ; this increase of thickness is principally 
in the external lamina, for when that is removed, the other 
appears equally so through its whole extent. 
To ascertain that the cornea is really thickest in the middle, 
I made a transverse section of it, and Mr. Ramsden, with se- 
veral other gentlemen, examined the cut edge through a mag- 
nifying glass, and all of them were satisfied with the fact of the 
central part being evidently thicker than that which was nearer 
to the circumference. 
It is necessary to mention, that in stretching the cornea 
the central part yields most readily to the power applied ; this 
is so much the case, that if the cut edge of the cornea is 
examined while it is several times drawn out and allowed to 
contract again, the change in the centre will be found the 
most distinct ; the principal elasticity appearing to reside in 
that part. 
Before these experiments were made upon the cornea, Mr. 
Ramsden had promised me that he would contrive an instru- 
ment by which the cornea might be examined, while the eye 
was adapting itself to different distances ; so as to enable us 
to decide whether any change took place at these times in its 
external figure. 
When I state to this learned Society, that seven months 
elapsed before the apparatus for this experiment was com- 
pleted, they will not attribute it to a want of solicitude on my 
part, or a want of attention in Mr. Ramsden ; but to delays 
which must necessarily occur to an artist so extensively em- 
ployed in business, and at the same time so ready to engage 
