4-12 



but he found their power of adaptation too far diminished by age for 

 such a trial. He however prevailed on Dr. Cutting, a young phy- 

 sician of his acquaintance, to make trial of it. The result was per- 

 fectly conformable to the supposition. The dilatation of the pupil, it 

 is true, commenced sooner than any other affection of the eye ; but 

 in the course of three quarters of an hour, the eye, which before the 

 experiment could see at six inches, could not now see at less than 

 three feet and a half : and when its pupil had acquired the greatest 

 dilatation, the rays from a candle, even at eight feet distance, could 

 not be made to converge on the retina, but only those from stars, or 

 from very distant lamps. The defect thus occasioned by belladonna 

 was found nearly in the same state on the following day ; and it was 

 not till the ninth day that the power of adapting the eye to near 

 objects was completely restored. During the whole of this time it 

 was observed that the affection was wholly confined to the left eye, on 

 which the experiment was made, and that the right eye remained 

 unaltered ; and in the same manner, when the experiment was after- 

 wards repeated on the right, the left was then wholly unaffected by 

 the belladonna. 



The next observations relate to the changes which naturally take 

 place in different eyes by age. With respect to those who are short- 

 sighted, it has been generally asserted by systematic writers, and 

 generally believed by others, that their eyes are rendered fitter for 

 seeing distant objects ; but Dr. Wells has observed, in various in- 

 stances, that this was not the case. 



One gentleman, a fellow of this Society, who was short-sighted in 

 early life, and consequently in the habit of using spectacles with 

 concave glasses constantly, could see with them perfectly at a great 

 variety of distances till he arrived at the age of fifty. But he then 

 began to observe that distant objects viewed through the glasses to 

 which he had been accustomed, were indistinct ; and he found it 

 necessary to use others which were more concave for seeing objects 

 at great distances. But along with this change of his sight, another 

 occurred of an opposite kind : for he now found, that when he wished 

 to examine minute objects attentively, it was necessary to remove his 

 spectacles entirely, and employ the naked eye alone. It was true, 

 therefore, that, with respect to near objects, he had become longer- 

 sighted, but in fact his range of vision was shortened equally at the 

 opposite extreme, so that the mean is little altered from what it 

 always has been. 



In a second instance the variation produced by age in a short-sighted 

 person was the same in kind, but not hitherto in so great degree. 



In a few trials which Dr. Wells has made upon short-sighted per- 

 sons with belladonna, the diminution of the range of adaptation has 

 not taken place at both extremities, but the power of seeing near 

 objects has alone been diminished. 



He is not, however, altogether satisfied with these experiments ; 

 and designs to pursue them further, and at some future time to com- 

 municate the results to the Society. 



