79 
on the Mechanism of the Eye. 
into the capsule, turn out the lens, and cut off the greater 
part of the posterior portion of the capsule, and of the rest 
of the vitreous humour. I next dissect the choroid and uvea 
from the sclerotica; and, dividing the anterior part of the cap- 
sule into segments from its centre, I turn them back upon the 
ciliary zone. The ciliary processes then appear, covered with 
their pigment, and perfectly distinct both from the capsule and 
from the uvea; (Plate VII. Fig. 54-) and the surface of the 
capsule is seen shining, and evidently natural, close to the base 
of these substances. I do not deny that the separation between 
the uvea and the processes, extends somewhat further back 
than the separation between the processes and the capsule ; but 
the difference is inconsiderable, and, in the calf, does not amount 
to above half the length of the detached part. The appearance 
of the processes is wholly irreconcileable with muscularity ; and 
their being considered as muscles attached to the capsule, is 
therefore doubly inadmissible. Their lateral union with the 
capsule, commences at the base of their posterior smooth sur- 
face, and is continued nearly to the point where they are more 
intimately united with the termination of the uvea ; so that, 
however "this portion of the base of the processes were disposed 
to contract, it would be much too short to produce any sensible 
effect. What their use may be, cannot easily be determined : 
if it were necessary to have any peculiar organs for secretion, 
we might call them glands, for the percolation of the aqueous 
humour ; but there is no reason to think them requisite for this 
purpose. 
The marsupium nigrum of birds, and the horse-shoe-like 
appearance of the choroid of fishes, are two substances which 
have sometimes, with equal injustice, been termed muscular. 
All the apparent fibres of the marsupium nigrum are, as 
