1,876.] ^L,f fHartahorne. 



the object, and we therefore say we see the object when only the projected, 

 retinal image is before our eyes." 



Against the hypothesis of the correction of inverse vision by experience, 

 we have, first, the clear and, so to speak, imperative testimony of every 

 one's consciousness; secondly, the very satisfactory observations and ex- 

 periments of Spalding and others, upon newly hatched chickens and new- 

 born pigs. The chicken just out of its shell, or one, after hatching, hooded 

 for a day or two and then allowed to see, will at once locate an object 

 brought near it (as an edible seed or grain), seizing it accurately with its 

 bill; and will, also, at once run in answer to the cluck of the hen, almost 

 always in a direct line. Similar facts, precisely, have been observed with 

 pigs immediately after their birth. Thus, in these animals, the non- 

 necessity of experience, even for the visual measurement of distances at 

 short range, is proved; much more then must it be impossible that experi- 

 ence should be needed to set things upright, they being inverted according 

 to actual vision. "While analogy here only affords a probability as to what 

 is true with regard to human sight, that probability is nevertheless very 

 strong indeed: not that correct visual impressions in all respects are C()?i(7e7i?- 

 tal with man, as our observation of infants does not seem to show; but that 

 at least the simpler elements of vision attend in their development the 

 maturity of the eye as an organ; and that among these elements, the sight 

 of objects as not inverted must be one of the simplest. If it be said that 

 the readiness for use of the senses and faculties of some new-born animals 

 is a result of hereditary transmission, a race-experience, accumulated 

 through long periods of time, I have nothing to say against this as, in itself, 

 a not improbable hypothesis, in regard to the mode of origin of such en- 

 dowments. But the idea of experience which is involved in the view just 

 above-mentioned, is quite different from this last. Experimentally acquired 

 corrections of positive sensory perceptions never go so far as to annul the 

 perception which has to be corrected, to such an extent that the process of 

 correction cannot Ije ascertained by consciousness. 



On the hypothesis that the inversion of the retinal images is effected 

 by a uniform decussation of the optic nerve-filaments, it is needful to re- 

 mark only three things: 1, that this must be a pure assumption, no such 

 mode or plan of arrangement of the filaments of the optic nerves being 

 anatomically discoverable; indeed, a much more general and intricate 

 plan of exchange of filaments, between eye and eye, optic ganglion and its 

 fellow, and all the parts of the two eyes and the two ganglia, having been 

 proved to exist; 2, that such an explanation is opposed to all the analogies 

 of nerve-distribution, in regard to the localization of impressions; the rela- 

 tive position of the HGVYe-trunk or its filaments, never affecting much if at 

 all, our perception of the locality of any sensation; all notions of locality or 

 direction, under normal circumstances, being obtained by means of, and at 

 the organ, not the transmitting or communicating nerve, of sense which is 

 concerned; 3, that the same reversal of position of the image or picture on the 

 retina produced by rays from an object seen, must occur horizontally as well 



