Rensselaer Republican, Volume 27, Number 26, Rensselaer, Jasper County, 5 March 1896 — OUR THIRD EYE. [ARTICLE]

OUR THIRD EYE.

Scientists Claim That We Have ' an Exira Optic., iThia i Recently Dbroyered Orxan Exists Abo in Vertebratea ol the Lower Orders-z Where It la . Located. \ Recent researches prove that man and all vertebrates seem to possess the rudiments of a third eyex This discovery is not only very interesting, but also remarkably instructive,smee the i rudimentary third.eye ot a man has. by one of the most noted philosophers of modern days, been looked upon as being the aeat of the soul. As or by proper use develop in strength and perfection, so they beeome weak by lack of use. If for many generations an organ should remain without use, its structure in time becomes simpler and more imperfect. If such a process continues throughout ages, an organ, by constant disuse, will become reduced to a mere rudiment of what it was in the species using the •same. Thus, species of birds that only walk and run, but never fly, have only rudimentary wings, as the ostrich; while in the eagle and the albatross the wings are seen In a state of perfection. Now, in closely examining the skulls cf certain lizards, it Was found that near the top of head, under the dark, opaque skin, and often, in the very bone, an almost perfect eye exists, although no ru.y of light ever could reach it. This eye shows a crystaline lens, a retina of very complex structure and an optic nerve; ip fact, all the essential parts of a perfect eye. But being covered by the opaque skin of the animal it is absolutely useless. If this optic nerve is traced to the brain it is found to connect the eye with the so-called pineal gland of the brain. This pineal gland, is, of course, in no sense of a word a real gland, but a definite portion of the nervous tissue of the brain, invariably located just back and partly over the cerebrum, and In front of the rounded brain-mass which generally is considered to correspond to the corpora quadrigemina in a man. This third eye of the spotted lizard is called the pineal eye, on account of the nerve connection of the retina witff the pineal gland. Now, while in certain lizards this highly developed eye is useless because it is covered by opaqtte sfcf*, and in others even deeply bedded bone, it would seem proba- ■ ble that Ik an earlier stage of development this pineal eye was not rudimentary, but iW constant use. A very slight modification W6uld accomplish this—namely, the transparency of the skin covering the eyV. This is exactly the condition of th* normal eyes In reptiles to-da®'; the ski® covers them, but it is transparent where it passes over "the eye. In the skulls df some of the gigantic reptiles of the earlier age bf this globe, paleontologists have long ago found n large round perforation. Probably this was the socket of the third or pineal eye of the ichthydsau- , rus. the plesiosaurus and the labyrinthodon. But a much more important conclusion mtist be drawn from this discovery—namely, that in all vertebrates, even including man, the traces of this third eye remain to-day. The pineal eye of lizards being connected with the large pineal gland of the same, it would seem that the pineal gland itself is but the nerve center or optic thalmus for this third eye. In all reptiles and amphibia the pineal gland is large; so it is also in fishes. In higher animals the cerebrum develops very much,.overgrowing the more posterior portions of the brain. By this preponderance of the nerve mass the pineal gland becomes covered by the cerebrum and assumes more and ntore rudimentary forms. But it remains with obstinate pertinacity. It is even always present iq man —though here only of the size of a pea and rudely resembling a pine cone in shape. It seems also degenerated in structure, having hardly any nervous tissue. These facts of form and structure have given rise to its name, that of pineal gland.—Popular Science Monthly- .