To the seven reports upon cases of persons born blind and afterward surgically treated, which are here presented in abridged form from the English originals, may be added some more recent and more accessible ones, one by Hirschberg ("Archiv fuer Opthalmologie," xxi, 1. Abth., S. 29 bis 42, 1875), one by A. von Hippel (ibid., xxi, 2. Abth., S. 101), and one by Dufour ("Archives des Sciences physiques et naturelles," lviii, No. 242, April, 1877, p. 420). The cases reported here are those most discussed. I have given them considerably in detail in order that the reader may form an independent judgment concerning the behavior of persons born blind and then operated upon, as that behavior is described _before_ the modern physiological controversy over empiricism and nativism. Helmholtz ("Physiologische Optik," Sec. 28) mentions, besides those of Chesselden and Wardrop and Ware, which he gives in abridged form, some other cases also. Others still may be found in Froriep's "Notizen" (xi, p. 177, 1825, and iv, p. 243, 1837, also xxi, p. 41, 1842), partly reported, partly cited (the latter according to Franz). In addition to the cases here given of persons born blind and then surgically treated--persons not able to see things in space-relations before becoming blind--one more case is to be mentioned; it is that of a girl who in her seventh year (probably in consequence of the effect of dazzling sunlight) lost her sight completely, but recovered it again at the age of seventeen years after being treated with electricity. She had to begin absolutely anew to learn to name colors like a child; all measure of distance, perspective, size, had been lost for her _by lack of practice_ (as O. Heyfelder relates in his work "Die Kindheit des Menschen," second edition, Erlangen, 1858, pp. 12-15). He says, p. 12, that the patient had been eight years blind; p. 13, that she had been ten years so. Such cases prove the great influence of experience upon vision in space, and show how little of this vision is inborn in mankind. When we compare the acquirement of sight by the normal newly-born child and the infant with that of those born blind, we should, above all, bear in mind that the latter in general could make use of only _one_ eye, and also that on account of the long inactivity of the retina and the absence of the crystalline lens, as well as in consequence of the numerous experiences of touch, essential differences exist. Notwithstanding this, there appears an agreement in the manner in which in both cases vision is learned, the eye is practiced, and the association of sight and touch is acquired. The seventh case in particular shows plainly how strong the analogies are.