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The Eye
dom has displayed in the structure of this beautiful organ; but the little that we know suffices to convince us of the admirable intelligence, goodness, and power of the Creator. In the first place, how fine is the disposition of the exterior parts of the eye, how admirably it is defended! Placed in durable orbits of bone, at a certain depth in the skull, they cannot easily suffer any injury; the over-arching eye-brows contribute much to the beauty and preservation of this exquisite organ; and the eye-lids more immediately shelter it from the glare of light, and other things which might be prejudicial; inserted in these are the eye-lashes, which also much contribute to the above effect, and also prevent small particles o dust, and other substances, striking against the eye.* The internal structure is still more admirable. The globe of the eye is composed of tunics, humours, muscles, and vessels, the coats are the cornea, or exterior membrane, which is transparent anteriorly, and opake posteriorly; the charoid, which is extremely vascular; the uvea, with the iris, which being of various colours, gives the appearance of differently coloured eyes; and being perforated, with the power of contraction and dilatation, forms the pupil; and, lastly, the retina, being a fine expansion of the optic nerve, upon it the impressions of objects are made. The humours are the aqueous, lying in the forepart of the globe, immediately under the cornea; it is thin, liquid, and transparent; the crystalline, which lies next to the aqueous, behind the uvea, opposite to the pupil, it is the least of the humours, of great solidity, and on both sides convex; the vitreous, resembling the white of an egg, fills all the hind part of the cavity of the globe, and gives the spherical figure to the eye. The muscles of the eye are six, and by the excellence of their arrangement it is enabled to move in all directions. Vision is performed by the rays of light falling on the pellucid and convex cornea of the eye, by the density and convexity of which they are united into a focus, which passes the aqueous humours, and pupil of the eye, to be more condensed by the crystalline lens. The rays of light thus concentrated, penetrate the vitreous humour, and stimulate the retina upon which the images of objects, painted in an inverse direction, are represented to the mind through the medium of the optic nerves. * Besides these, amongst the internal parts are enumerated, the lachrymal gland, which secretes the tears; the lachrymal caruncle, a small fleshy substance at the inner angle of the eye; the puncta lachrymalia, two small openings on the nasal extremity of each eye-lash; the lachrymal duct, formed by the union of the ducts leading from the puncta lachrymalia, and conveying the tears into the nose; the lachrymal sac, a dilatation of the lachrymal canal. -The visual orbs Remark, how aptly station'd for their task; Rais'd to th' imperial head's high citadel, A wide extended prospect to command.
See the arch'd outworks of impending lids, With hairs, as palisadoes fenc'd around To ward annoyance from without.
Bally.
Again :- Who form'd the curious organ of the eye, And cloth'd it with its various tunicles, Of texture exquisite; with crystal juice Supply'd it, to transmit the rays of light; Then plac'd it in its station eminent, Well fenc'd and guarded, as a centinel To watch abroad, and needful caution give?
Needler.
The next subject is, THE CURIOUS STRUCTURE OF THE EAR.
The channel'd ear, with many a winding maze, How artfully perplex'd, to catch the sound.
And from her repercussive caves augment!
Dark night, that from the eye his function takes, The ear more quick of apprehension makes; Wherein it doth impair the seeing sense, It pays the HEARING-double recompense.
Bally.
Shakspeare.
Although the ear, with regard to beauty, yields to the eye, its conformation is not less perfect, nor less worthy of the Creator. The position of the ear bespeaks much wisdom; for it is placed in the most convenient part of the body, near to the brain, the common seat of all the senses. The exterior form of the ear merits considerable attention; its substance is between the flexible softness of flesh, and the firmness of bone, which prevents the inconvenience that must arise from its being either entirely muscular or wholly formed of solid bone. It is therefore cartilaginous, possessing firmness, folds, and smoothness, so adapted as to reflect sound; for the chief use of the external part is to collect the vibrations of the air, and transmit them to the orifice of the ear. The internal structure of this organ is still more remarkable. Within the cavity of the ear is an opening, called the meatus auditorius, or auditory canal, the entrance to which is defended by small hairs, which prevent insects and small particles of extraneous matter penetrating into it; for which purpose there is also secreted a bitter ceruminous matter, called ear-wax. auditory canal is terminated obliquely by a membrane, generally known by the name of drum, which instrument it in some degree resembles; for within the cavity of the auditory canal is a kind of bony ring, over which the membrana tympani is stretched. In contact with this membrane, on the inner side is a small bone (malleus) against which it strikes The