the brain sensation (sight) results, which refers the irritant right back along the ray-line of each pencil to its source. So point after point irritates the retina, and is referred to its appropriate place in space until the luminous object is reproduced in the external world by the outward projection of an infinite number of luminous points.

To make this clear, a very simple object should be used; let it be a vertical line. (Fig. 4.) Now a lumi

B

C

FIG. 4.- THE OUTWARD PROJECTION OF THE Retinal IMAGE.

nous point at the top of this line produces an irritant point at the lower side of the retina, which is referred back to its source above and seen there in space.

A luminous point at the bottom of this line produces an irritant point on the upper side of the retina, and is referred back to its position in space, which is below. A point from the center is referred back to its place in the centre for the same reason. And so with a point midway from the center to the top, and a point midway from the center to the bottom; and the process goes on simultaneously for each point of which the line is composed, and a sort of mental composite results, which is the exact counterpart of the object, occupying the identical position in space;

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somewhat as a spiritual body is conceived to be immanent in the natural body.

The solid lines represent the pencils of rays, the broken lines the axial rays of each pencil, showing the direction of the outward reference of the three irritant points illustrated.

To recapitulate: By the law of conjugate foci, a luminous point in space corresponds to an irritant point on the retina. By the law of outward projection it is referred to its proper place in the object, and, as the object is not seen as a whole, an infinite number of such luminous points of which the object is composed are referred to their respective positions, and furnish a synthetic conception, which must be erect because each of its constituent points is in its place.

Since Newton, scientists have recognized that for one body to act upon another at a distance, some medium must intervene. So with sight, the provisional ether is that intermediate something which reaches from the luminous point and "touches" the retina. The unlimited extent of the ether gives to sight unlimited range, and, altho light travels 186,000 miles per second, it takes three and a half years for light to reach us from the nearest star.

Professor Dolbear says: "The light which reaches us to-day from some of the more distant stars left them before America was discovered; before Jesus was born; before the pyramids were built,

and, for all we should be able to see, they may have ceased to exist long ago, tho their light still shines." I

While this work was in press there appeared in Current Literature, September, 1906, an article entitled "A New Theory of Vision." This was a quotation from Cosmos, Paris, of the work of Mr. George Poullaine, who claimed to have discovered " a loop or twist in the optic nerve." The twist is in the protuberance of the outer and posterior parts of the optical layer of the brain. "The peculiar conformation explains," says Cosmos, "the reinversion of the retinal image.

"The optic nerves, after emerging from the eyeballs, converge to the optic chiasma. Here they partly cross, or seem to exchange part of their fibers. The two nerve bundles thus modified separate and pass around the peduncles. In this part of their course they are known as the optical bands or Gasset's hemopic nerves.

"These bands enter the brain. Their fibers can be traced in the pulvinar, where they describe concentric curves. They can be traced also in other portions of the optical layer, where they are known as Gratiolet's optic rays.

"In order to more correctly ascertain the paths of the fibers, Poullaine studied and measured sections of the loop made by a horizontal plane and by two vertical planes, anterior, posterior, and transverse. Matter, Ether, and Motion.

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. . . The theory," according to Cosmos, "makes it easy to understand the mechanism of the reinversion of the retinal image. The double curve effects a complete reversal of the order of the nerve fibers both from top to bottom and from right to left, the two half-turns being exactly equivalent to a halftwist or rotation thru 180 degrees about the axis of the bundle."

Individual anatomical variations of all parts of the human body are frequently discovered by surgeons. The location and number of the branches of the arteries, veins, and nerves are not the same in different individuals. Is it reasonable to presume that the optic nerves are an exception to this rule? If not, then there are many people whose optic nerves do not twist the exact 180 degrees required.

If erect vision depends upon this condition, it is evident that a faulty or anomalous development would furnish instances of partial or complete inverted vision. Very many cases of this kind are needed to substantiate this very ingenious theory, and none are given. Moreover, the theory is based on the misconception that we see the image, not on the retina, as the tactile reinversion theory presumes, but at some other portion of the cranium. In a very recent work Doctor Souter says: "It is apparent that the retinal image is always inverted with respect to the object of vision. The mind, however, takes no cognizance of this inversion, since it possesses the power of exter

nal projection so that we see not the image but the object in its true position." I

Then the writer proceeds to repeat the old argument of tactile reinversion as follows: "This power has doubtless been derived thru association with the sense of touch. We have learned that a stimulus conveyed to the brain from the upper part of the retina proceeds from an object situated below the eye, and vice versa, and that a stimulus on the temporal side of the retina must proceed from an object on the nasal side of the eye, and vice versa.”

'The Eye and Nervous System. Posey and Spiller. Lippincott, April, 1906, p. 35.