OBSERVATIONS AND EXPERIMENTS ON VISION. 329 



fhe first experiment ; and that he probably, ia consequence 

 of my example, applied no more when he made the se- 

 cond ; as this might have been the reason, that during both 

 experiments he retained, in part, the capacity of adapting 

 his eyes to different distances. 



The experiment on Mr. Patrick was conducted by Inyself, Another expe- 

 after he had been frequently exercised in observing the ex- ""^^"^ • 

 tent of his perfect vision. The results were similar to those 

 which had been remarked by Dr. Cutting. The power of 

 alteriTig the adaptation 'of his eye, according to the disfancc 

 of the objects viewed, was for some time entirely lost, and his 

 sight became accurately fitted for such only, as were placed 

 at the farther extremity of his former range of perfect vi- 

 sion. While one eye vvas under the influence of the bella- The juice af- 



donna, the vision of the other was unaffected. fected only the 



' eye apphed to. 



From these experiments it seems probable, that belladonna Did not pro- 

 will in no case produce the same effect upon a young short- ^"^^J^^^ eifects 

 sighted person, that age has produced in the two instances of 

 which I have spoken. I expect, however, to have an op- Farther expe- 

 portunity of repeating the experiment on two persons, who ''iniemsto be 

 are very considerably short-sighted ; and I shall take the 

 liberty of communicating the result to the Royal Society, 

 together with some observations I have already made, and 

 others which I hope to make, respecting those persons, who Power of the 

 seem to retain to extreme old age the power of seeing per- ^^ ^[^^a'e^ 

 fectly, as far as the accommodating power of the eye is con- 

 cerned, both distant and near objects ; and of others, who, 

 after being without this power for many years, appear to or recovered, 

 regain it at a similar period of life. Probably the making 

 known my intention may facilitate its accomplishment, by 

 inducing other Fellows of the Society to furnish me with 

 opportunities of increasing my knowledge of these subjects. 

 In the mean time, I shall offer a few words upon two other 

 topics in vision, which seem to derive illustration from my 

 experiments with belladonna. 



V. 1. Not only do the pupils move together, when both Moving of both 

 eyes are in a healthy state, but the pupil of one eye affected P"P' ^'^°g^' ^^> 

 ■with gutta Serena moves with the pupil of the other, as long 

 as this remains sound. These facts are generally, but in not owing to 

 na^ opinion erroneously, attributed to the immediate sym- j'^^'J^^ '^^esym- 



pathy 



