294 THOMAS YOUNG. 
Among the different modes of obtaining distinct images, 
nature has assuredly made a choice, since man can see 
with great distinctness at very different distances. The 
question thus put has afforded a wide subject of remark 
and discussion to physicists, and great names have figured 
in the debate. 
” Kepler and Descartes held that the whole ball of the 
eye is susceptible of being elongated and flattened. 
Porterfield and Zinn contended that the crystalline 
lens was movable; and that it could place itself nearer 
to, or further from the retina, as might be needed. 
Jurin and Musschenbroeck believed in a change in the 
curvature of the cornea. 
Sauvages and Bourdelot supposed also that a change 
in curvature took place, but only in the crystalline lens. 
Such is also the system of Young. Two memoirs which. 
our colleague successively submitted to the Royal Society 
of London include the complete development of his views. 
In the first of these, the question is treated almost 
entirely in an anatomical point of view. Young there 
demonstrates by the aid of direct observations of a very 
delicate kind, that the crystalline is endowed with a 
fibrous or muscular constitution, admirably adapted to 
all sorts of changes of form. This discovery overthrew 
the only solid objection which had, till then, opposed the 
hypothesis of Sauvages and Bourdelot. 
That hypothesis had no sooner been announced than it 
had been attacked by Hunter. 
Thus this celebrated anatomist aided the cause of the 
young experimenter by the attention drawn to the sub- 
ject, while his labours were as yet unpublished, and not 
even communicated to any one. However, this point of 
the discussion soon lost its importance. The learned 
