The principles of psychology . he correct perception to victory. The bareidea of the right object is itself a feeble reproduction which with thehelp of the proper retinal picture develops into clear and lively sensa-tion. But if there be not already in the nervous apparatus a disposi- THE PERCEPTION OF SPACE. 263 tion to the production of that percept which our judgment tells us isright, our knowledge strives in vain to conjure up the feeling of it;we then know that we see something to which no reality corresponds,but we see it all the same. * Note that no object not probable, no object lohicl
The principles of psychology . he correct perception to victory. The bareidea of the right object is itself a feeble reproduction which with thehelp of the proper retinal picture develops into clear and lively sensa-tion. But if there be not already in the nervous apparatus a disposi- THE PERCEPTION OF SPACE. 263 tion to the production of that percept which our judgment tells us isright, our knowledge strives in vain to conjure up the feeling of it;we then know that we see something to which no reality corresponds,but we see it all the same. * Note that no object not probable, no object lohicli we are notincessantly practised in reproducing, can acquire this vividnessin imagination. Objective corners are ever changing theirangles to the eyes, spaces their apparent size, lines theirdistance. But by no transmutation of position in spacedoes an objective straight line appear bent, and only in oneposition out of an infinity does a broken line look , it is impossible by projecting the after-image A B. Fig. 77. of a straight line upon two surfaces which make a solidangle with each other to give the line itself a sensible*kink. Look with it at the corner of your room: theafter-image, which may overlap all three surfaces of thecorner, still continues straight. Volkmann constructed acomplicated surface of projection like that drawn in , but he found it impossible so to throw a straight after-image upon it as to alter its visible form. * Hermanns Handb. der Physiologie. in. 1, p. 565-71. 264 P8YCE0L0QT. One of tlie situations in which we oftenest see things isspread out on the ground before us. We are incessantlydrilled in making allowance for this perspective, and reduc-ing things to their real form in spite of optical foreshorten-ing. Hence if the preceding explanations are true, weought to find this habit inveterate. The lower half of theretina, which habitually sees the farther half of thingsspread out on the ground, ought to have acquired a habi
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectpsychology, bookyear1
