THE PERCEPTION OF SPACE. 148 



occasionally produce not wliollj dissimilar results. Panum, 

 the German physiologist, relates that when, as a boy, he 

 was etherized for neuralgia, the objects in the room grew 

 extremely small and distant, before his field of vision dark- 

 ened over and the roaring in his ears began. He also men- 

 tions that a friend of his in church, struggling in vain to 

 keep awake, saw the preacher grow smaller and smaller 

 and more and more distant. I myself on one occasion 

 observed the same recession of objects during the begin- 

 ning of chloroformization. In various cerebral diseases 

 we find analogous disturbances. 



Can we assign the physiological conditions ivhich make the 

 elementary sensible largeness of one sensation vary so much from 

 that of another ? Only imperfectly. One factor in the re- 

 sult undoubtedly is the number of nerve-terminations 

 simultaneously excited by the outward agent that awakens 

 the sensation. When man}' skin-nerves are warmed, or 

 much retinal surface illuminated, our feeling is larger than 

 when a lesser nervous surface is excited. The single sen- 

 sation yielded by two compass-points, although it seems 

 simple, is yet felt to be much bigger and blunter than that 

 yielded by one. The touch of a single point may always 

 be recoguized by its quality of sharpness. This page looks 

 much smaller to the reader if he closes one eye than if both 

 eyes are open. So does the moon, which latter fact shows 

 that the phenomenon has nothing to do with parallax. 

 The celebrated boy couched for the cataract by Cheselden 

 thought, after his first eye was operated, " all things he saw 

 extremely large," but being couched of his second eye, 

 said " that objects at first appeared large to this eye, but 

 not so large as they did at first to the other ; and looking 

 upon the same object with both eyes, he thought it looked 

 about twice as large as with the first couched eye only, but 

 not double, that we can anyways discover." 



The greater extensiveness that the feeling of certain 

 parts of the same surface has over other parts, and that 

 one order of surface has over another (retina over skin, for 

 example), may also to a certain extent be explained by the 

 operation of the same factor. It is an anatomical fact that 

 the most spatially sensitive surfaces (retina, tongue, finger- 



