a Sana aT Crystalline Lens in Man. 133 
outer surface of the ciliary body and choroid. These fibres are 
connected in front with the middle of the three divisions of the 
posterior elastic lamina of the cornea (the inner division of this lamina 
spans the margin of the anterior chamber and forms the pillars of 
the iris, and the outer division passes backwards and outwards to 
the sclerotic behind the space known as the circulus venosus, or 
Schlemm’s Canal). 
The shortening of these meridional bundles of muscular fibre 
will tend to approximate their corneal and choroidal attachments ; 
and if we regard the corneal one as the more fixed point, a view 
which best harmonizes with the anatomical facts, the contraction of 
these bundles tends to draw the choroid forward and tighten it 
upon its contents. According to this view the ciliary muscle (as 
regards its radial bundles) is a tensor of the choroid, as Briicke 
named it. 
Let us next see what light these anatomical data throw on the 
process of accommodation. You will recollect that im accommoda- 
tion for a nearer object the lens, as a whole, does not shift its place, 
but its anterior surface becomes notably more convex, and the con- 
vexity of its posterior surface is very slightly increased. With this 
alteration of its figure the axis is lengthened and the transverse dia- 
meter shortened. The pupillary region of the iris approaches the 
cornea, and the circumference of the iris retreats from it. The lens, 
with its capsule, is elastic, but without contractile irritability ; its 
role is passive. When the suspensory ligament is tight, it must 
exert traction on both surfaces of the lens (chiefly on the front, by 
reason of the greater stoutness of the fibres, and of their attachment 
to the lens advancing rather farther from the edge of the lens), 
tending to compress the lens in the direction of its axis, and to 
flatten it—the shape of the lens, in looking at a distant object, which 
is a passive act, not requiring accommodation. 
When the radial or longitudinal bundles of the ciliary muscle 
contract, and the distance between their extreme points of attach- 
ment is lessened, the previously tense suspensory ligament is re- 
laxed, and the lens, no longer compressed by it, becomes more convex 
by virtue of its own elasticity. If at the same time the circular 
bundles of the muscle were to shorten, this would tend to contract 
_ the circle of the ciliary processes, by which the suspensory ligament 
would be still more slackened ; I doubt, however, whether they can 
act as a compressor of the edge of the lens. 
The ciliary muscle derives its nerves from the lenticular gan- 
glion. They pierce the sclerotic, not far from the optic nerve, and 
gaining the inner surface of this coat, they run forwards between 
it and the choroid till they reach the ciliary muscle, on the outer 
surface of which they break up and re-combine in the well-known 
