73 
on the Mechanism of tide Eye. 
whole on an experiment borrowed from Barrow, which with 
me has totally failed ; and I cannot but agree with Dr. Olbers 
in the remark, that it is easier to confute him than to understand 
him. He argued for a partial change of the figure of the lens ; 
and perhaps the opinion was more just than the reasons adduced 
for its support. Lobe', or rather Albinus,* decidedly favours 
a similar theory ; and suggests the analogy of the lens to the 
muscular parts of pellucid animals, in which even the best 
microscopes can discover no fibres. Camper also mentions 
the hypothesis with considerable approbation . -f Professor Reil 
published, in 1793, a Dissertation on the Structure of the Lens ; 
and, in a subsequent paper, annexed to the translation of my 
former Essay in Professor Gren's Journal, § he discussed the 
question of its muscularity. I regret that I have not now an 
opportunity of referring to this publication ; but I do not recol- 
lect that Professor Reil's objections are different from those 
which I have already noticed. 
Considering the sympathy of the crystalline lens with the 
uvea, and the delicate nature of the change of its figure, there 
is little reason to expect that any artificial stimulus would be 
more successful in exciting a contractive action in the lens, than 
it has hitherto been in the uvea ; much less would that contrac- 
tion be visible without art. Soon after Mr. Hunter's death, I 
pursued the experiment which he had suggested, for ascertain- 
ing how far such a contraction might be observable. My appa- 
ratus (Plate V. Fig. 27.) was executed by Mr. Jones. It 
consisted of a wooden vessel blacked within, which was to be 
* De quibusdam Oculi Partibus, L. B. 1746. Ap. Hall. Disp. Anat. IV". p. 301. 
t De Oculo Humano. L. B. 1742. Ap. Hall. Disp. Anat. VII. 2. p. 108, 109. 
$ 1794 * P- 35 2 > 354 * 
MDCCC1. L 
