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This arrangement brings the elastic force of the eyeball into opposition to the elastic force of the lens. The ciliary muscle plays between these opposing forces in the following manner: To thicken the lens, the ciliary muscle contracts, pulling forward the suspensory ligament and releasing its tension on the membranous capsule. This enables the lens to thicken on account of its own elastic force.
We have to take into account the large scleral wound made, and the fact that this lies close to the ciliary body. The sudden release of all tension and the simultaneous weakening of the supports of the lens and vitreous body create very unfavorable conditions under which to make the crucial step of the operation.
It is dark in color and fragile in structure, and is made up almost entirely of blood-vessels and nerves. As the choroid approaches the front part of the eyeball, its parts become folded upon themselves into a series of ridges, called ciliary processes. These folds gradually become larger, and at last merge into the ciliary or accommodation muscle of the eye.
Though in those microscopic Protophyta and Protozoa inhabiting the water the spores of algæ, the gemmules of sponges, and the infusoria generally we see locomotion produced by ciliary action; yet this locomotion, while rapid relatively to their sizes, is absolutely slow.
Snell reports a case in which a piece of steel was imbedded and encapsulated in the ciliary process twenty-nine years without producing sympathetic irritation of its fellow, but causing such pain as to warrant enucleation of this eye.
Presently one of the trees as I must call them unfolded a long ciliary process, with which it seized one of the gleaming fruits that glittered on its summit, and sweeping slowly down, held it within reach of Animula. The sylph took it in her delicate hand, and began to eat.
However this obstruction may be brought about, whether by thickening of the iris root during dilatation of the pupil, pushing forward of the iris root by the larger ciliary processes of age, or the enlarged crystalline lens pressing on the ciliary processes; or by inflammatory adhesion of the iris to the filtration area; ballooning of the iris, or its displacement by traumatic cataract; or adhesion to the cornea after perforating ulcer in the secondary glaucomas; or whether the obstruction is due to the accumulation of experimental precipitates, as shown by Schreiber and Wengler, or possibly of pigment granules into Fontana's space; or a process of sclerosis closing the spaces by contraction of new-formed connective tissue, or the covering over with proliferating implanted epithelium following injury opening the anterior chamber; glaucoma follows impairment of this drainage space, and lessened outflow through it.
This important fact justifies us in concluding, in accordance with the biogenetic law, that their ancestors also were phylogenetically developed from a similar stem-form. This ancient stem-form is the gastraea. The gastraea probably lived in the sea during the Laurentian period, swimming about in the water by means of its ciliary coat much as free ciliated gastrulae do to-day.
I admit that this intervention exposes the root of the iris and the ciliary body, but I have never yet had the slightest infection of the wound.
Clay Wallace of New York, who published a very ingenious little book on the eye about twenty years ago, with vignettes reminding one of Bewick, was among the first, if not the first, to describe the ciliary muscle, to which the power of adjustment is generally ascribed.