Page:Popular Science Monthly Volume 21.djvu/340

328 cutting of his knife—that is, that he unconsciously puts it in the right position.

Practice further exhibits its influence upon the nervous system on its purely sensory side, abstracted from all movement. It sharpens and corrects the musical ear, and teaches it to perceive over-tones, in-exact intervals, and slight dissonances. The local sense and the color sense of the eye are improved by practice. It teaches the wonderful arts of quick reading, of taking in fleeting phenomena like the vibrations of the magnetic needle, of bringing the sight of the gun to bear on the black of the target. It teaches to distinguish copies and all kinds of subjective appearances, to comprehend at a glance microscopic pictures that pass before the beginner in superficial confusion, in such a way that it is very hard to draw the line between exercise of the sense and that exercise of the judgment over the impressions of sense that is called visus eruditus. As exercise induces the discontinuance of unused muscles, it also teaches us to neglect unused images, such as the double images of the points of the picture outside of the horopter; or, in looking through an optical instrument, the impressions made upon the unengaged eye. Yet no practice appears to break through the law according to which the points of the retina in indirect vision receive attention only transiently and with a certain effect. Although it is hardened against bad smells, the nose of the chemist is the rival of spectrum analysis in delicacy. It would be unjust to say that the wine-connoisseurs of Bordeaux can discriminate concerning the place of the growth of a vintage, while only its age is in question with them. Not less susceptible of cultivation are the perceptions of temperature, pressure, and locality. The last, especially, measured according to the least distance at which two bodies, nearly in contact, still separate, may be distinguished, become sharpened by practice in the course of a few days—giving one of the arguments which oppose a purely anatomical definition of the range of feeling.

As exercise refines the senses, neglect stupefies them, and that not merely in consequence of the apathy of the organ. After destroying the eyes and ears of new-born puppies, Herr Hermann Munk observed that what he had recognized as the visory and auditory spheres of the brain borders were backward in development. According to Huguenin, blindness of many years' duration results in waste of the visory spheres.



N our journey from Sayang in Yunnan to Bhamo in Burmah, we became acquainted with a race of mountaineers who are called Kacheen by the Burmese, but who call themselves Chingpos. They 