Dr. Wells’s Observations 
39 ° 
ago,* with what it was after I had lost the power of altering' 
their refractive state ; but though I found no difference, yet, 
as their coats might have in the mean time become more rigid, 
I thought it right to have the experiment repeated, in a man- 
ner to which no objection could be taken. 
The only other part of the eye, or its appendages, which 
remains for enabling us to see equally well at very different 
distances, is the crystalline ; and that it does produce this 
effect, either wholly, or very nearly so, is manifest, from the 
necessity even young persons are under, who have lost it, of 
using glasses of very different convexities for near and remote 
objects. But in what way this important office is performed 
by it seems still unknown. The learned Dr. Young, indeed, 
as well as others before him, has supposed, that the crystal- 
line has the power of altering its figure; but the proofs hither- 
to given in favour of this opinion appear very defective. In 
1794, 1 attempted to submit its justness to the test of direct 
experiments, by applying to the crystallines of oxen, which 
had been felled from thirty seconds to a minute before, che- 
mical and mechanical stimuli, and those of Galvanism and 
electricity ; but in no instance was any alteration of figure, or 
other indication of muscular power, observed. All of these 
stimuli were applied to the crystalline while it was surrounded 
by air, and some of them while it was covered with warm 
water. Last summer, after I knew that men lose, from in- 
crease of years, the faculty of altering the refractive state of the 
eye, I thought it possible, that the oxen on which I had made 
the experiments were too old for them. I therefore repeated 
most of them on the crystallines of a calf and a lamb ; but 
* Essay on Single Vision, &c. p. 136, 
