on the Mechanism of the Eye. 75 
filaments at the same place. The branches often re-unite, with 
a slight protuberance, that scarcely deserves the name of a 
ganglion : here they are tied down, and mixed with the hard 
whitish-brown membrane that covers the compact spongy sub- 
stance, in which the vessels of the ciliary processes anastomose 
and subdivide. (Plate VI. Fig. 47.) The quantity of the 
nerves which proceeds to the iris, appears to be considerably 
smaller than that which arrives at the place of division : hence 
there can be little doubt that the division is calculated to supply 
the lens with some minute branches ; and it is not improbable, 
from the appearance of the parts, that some fibres may pass to 
the cornea ; although it might more naturally be expected, that 
the tunica conjunctiva would be supplied from without. But 
the subdivisions which probably pass to the lens, enter imme- 
diately into a mixture of ligamentous substance and of a tough 
brownish membrane; and I have not hitherto been able to 
develope them. Perhaps animals may be found in which this 
substance is of a different nature ; and I do not despair that, 
with the assistance of injections, for more readily distinguishing 
the blood vessels, it may still be possible to trace them in 
quadrupeds. Our inability to discover them, is scarcely an 
argument against their existence : they must naturally be deli- 
cate and transparent; and we have an instance, in the cornea, 
of considerable sensibility, where no nerve has yet been traced. 
The capsule adheres to the ciliary substance, and the lens to 
the capsule, principally in two or three points ; but I confess, I 
have not been able to observe that these points are exactly 
opposite to the trunks of nerves ; so that, probably, the adhesion 
is chiefly caused by those vessels which are sometimes seen 
passing to the capsule in injected eyes. We may, however, 
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