Apart from its uses, the eye itself is an interesting and instructive object of study. It presents beyond comparison the most beautiful example of design and artistic workmanship to be found in the bodily structure. It is the watchful sentinel and investigator of the external world. Unlike the senses of taste and smell we seem, by the sense of vision, to become aware of the existence of objects which are entirely apart from us, and which have no direct or material link connecting them with our bodies. And yet we are told that in vision the eye is affected by something which is as material as any substance we taste or smell. Note. “The higher intelligence of man is intimately associated with the perfection of the eye. Crystalline in its transparency, sensitive in receptivity, delicate in its adjustments, quick in its motions, the eye is a fitting servant for the eager soul, and, at times, the truest interpreter between man and man of the spirit’s inmost workings. The rainbow’s vivid hues and the pallor of the lily, the fair creations of art and the glance of mutual affection, all are pictured in its translucent depths, and transformed and glorified by the mind within. Banish vision, and the material universe shrinks for us to that which we may touch; sight alone sets us free to pierce the limitless abyss of space.”—M’Kendrick and Snodgrass’s _Physiology of the Senses_. Physicists tell us that this material, known as the _luminiferous ether_, permeates the universe, and by its vibrations transmits movements which affect the eye, giving rise to the sensation of light, and the perception of even the most distant objects. Our eyes are so constructed as to respond to the vibrations of this medium for the transmission of light. 325. The Eye. The eye, the outer instrument of vision, is a most beautiful and ingenious machine. All its parts are arranged with such a delicate adjustment to one another, and such an exquisite adaptation of every part to the great object of the whole, that the eye is properly regarded as one of the wonders of nature. The eyeball is nearly spherical in shape, but is slightly elongated from before backwards. The front part is clear and transparent, and bulges somewhat prominently to allow the entrance of the rays of light. The eye rests in a bowl-shaped socket, called the orbit, formed by parts of various bones of the head and face. The margins of this cavity are formed of strong bone which can withstand heavy blows. The socket is padded with loose, fatty tissue, and certain membranes, which serve as a soft and yielding bed in which the eyeball can rest and move without injury. In a severe sickness this fatty tissue is absorbed, and this fact explains the sunken appearance of the eyes.