on the Mechanism of the Eye. 63 
would be impossible in a living eye. Dr. Olbers also mentions 
an observation of Professor Wrisberg, on the eye of a man 
whom he believed to be destitute of the power of accommoda- 
tion in his life-time, and whom he found, after death, to have 
wanted one or more of the muscles : but this want of accom- 
modation was not at all accurately ascertained. I measured, in 
the human eye, the distance of the attachment 0} the inferior 
oblique muscle from the insertion of the nerve : it was one-fifth 
of an inch ; and from the centre of vision not a tenth of an 
inch ; so that, although the oblique muscles do in some positions 
nearly form a part of a great circle round the eye, their action 
would be more fitted to flatten than to elongate it. We have 
therefore reason to agree with Winslow, in attributing to them 
the office of helping to support the eye on that side where the 
bones are most deficient: they seem also well calculated to 
prevent its being drawn too much backwards by the action of 
the straight muscles. And, even if there were no difficulty in 
supposing the muscles to elongate the eye in every position, yet 
at least some small difference would be expected in the extent 
of the change, when the eye is in different situations, at an 
interval of more than a right angle from each other; but the 
optometer shews that there is none. 
Dr. Hosack alleges that he was able, by making a pressure 
on the eye, to accommodate it to a nearer object : * it does not 
appear that he made use of very accurate means of ascertaining 
the fact ; but, if such an effect took place, the cause must have 
been an inflection of the cornea. 
It is unnecessary to dwell on the opinion which supposes a 
joint operation, of changes in the curvature of the cornea and 
* Phil. Trans, for 1794. p. 212. 
