he question of how this network ever gets"wired" together is very interesting The problem of how much is already wired and how much is learned is an old one It used to be thought long ago that perhaps it does not have to be wired carefully at all, it is only just roughly interconnected, and then, by experience, the young child learns that when a thing is "up there "it produces some sensation in the brain Doctors always tell us what the young child"feels, but how do they know what a child feels at the age of one?)The child, at the age of one, supposedly sees that n object is"up there, gets a certain sensation, and learns to reach"there because when he reaches"here, "it does not work. That approach probably is not correct, because we already see that in many cases there are these special detailed interconnections. More illuminating are some most remarkable experiments done ith a salamander. (Incidentally, with the salamander there is a direct crossover connection, without the optic chiasma, because the eyes are on each side of the head and have no common area. Salamanders do not have binocular vision. The experi ment is this. We can cut the optic nerve in a salamander and the nerve will grow out from the eyes again. Thousands and thousands of cell fibers will thus re-establish themselves. Now, in the optic nerve the fibers do not stay adjacent to each other-it is like a great, sloppily made telephone cable, all the fibers twisting and turning, but when it gets to the brain they are all sorted out again. When we cut the optic nerve of the salamander, the interesting question is, will it ever get straightened out? The answer is remarkable: yes. If we cut the optic nerve of the salamander and it grows back, the salamander has good visual acuity again. However, if we cut the optic nerve and turn the eye upside down and let it grow back again, it has good isual acuity all right, but it has a terrible error: when the salamander sees a fly ap here, it jumps at it"down there, and it never learns. Therefore there is some mysterious way by which the thousands and thousands of fibers find their right places in the brail This problem of how much is wired in, and how much is not, is an important problem in the theory of the development of creatures. The answer is not known but is being studied intensively The same experiment in the case of a goldfish shows that there is a terrible not, like a great scar or complication, in the optic nerve where we cut it, but in spite of all this the fibers grow back to their right places in the brain. In order to do this, as they grow into the old channels of the optic nerve they must make several decisions about the direction in which they should grow. How do they do this? There seem to be chemical clues that different fibers respond to differently. Think of the enormous number of growing fibers, each of which is an ndividual differing in some way from its neighbors; in responding to whatever the chemical clues are, it responds in a unique enough way to find its proper place for ultimate connection in the brain! This is an interesting-a fantastic-thing It is one of the great recently discovered phenomena of biology and is undoubtedly connected to many older unsolved problems of growth, organization, and develop ment of organisms, and particularly of embryos One other interesting phenomenon has to do with the motion of the eye. The eyes must be moved in order to make the two images coincide in different cumstances. These motions are of different kinds: one is to follow something, which requires that both eyes must go in the same direction, right or left, and the othel point them toward the same place at various distances away, which requires that they must move oppositely. The nerves going into the muscles of the eye are already wired up for just such purposes. There is one set of nerves which will pull the muscles on the inside of one eye and the outside of the other, and relax the opposite muscles, so that the two eyes move together. There is another center where an excitation will cause the eyes to move in toward each other from parallel Either eye can be turned out to the corner if the other eye moves toward the nose, but it is impossible consciously or unconsciously to turn both eyes out at the same time, not because there are no muscles, but because there is no way to send a signal to turn both eyes out, unless we have had an accident or there is something the matter, for instance if a nerve has been cut. Although the muscles of certainly steer that eye about, not even a Yogi is able to move both eyes out freely 36-5