TEE PERCEPTION OF SPACE. 201 



muscles of the body at large we find the same vagueness. 

 Goldscheider found that the minimal perceived rotation of 



size depend on a comparison of the intensity of the feelings of movement 

 which arise in our eyeball-muscles as we glance over the distance, and 

 which fuse with the sensations of light" (p. 143). The facts upon which 

 the conclusion is based are certain constant errors which Mimsterberg 

 found according as the standard or given interval was to the right or the 

 left of the interval to be marked off as equal to it, or as it was above or 

 below it, or stood in some more complicated relation still. He admits that 

 he cannot explain all the errors in detail, and that we "stand before results 

 which seem surprising and not to be unravelled, because we cannot analyze 

 the elements which enter into the complex sensation which we receive." 

 But he has no doubt whatever of the general fact " that the movements of 

 the eyes and the sense of their position when tixed exert so decisive aa 

 influence on our estimate of the spaces seen, that the errors cannot possi- 

 bly be explained by anything else than the movement-feelings and their 

 reproductions in the memory" (pp. 1(56, 167). It is presumiituous to doubt 

 a man's opinion when you haven't had his experience ; and yet there are a 

 number of points which make me feel like suspending judgment in regard 

 to Herr M.'s dictum. He found, for example, a constant tendency to under- 

 estimate intervals lying to the right, and to overestimate intervals lying 

 to the left. He ingeniously explains this as a result of the habit of read- 

 ing, which trains us to move our eyes easily along straight lines from left 

 to right, whereas in looking from right to left we move them in curved 

 lines across the page. As we measure intervals as straight lines, it costs 

 more muscular effort to measure from right to left than the other way, 

 and an interval lying to the left seems to us consequently longer than it 

 really is. Now I have been a reader for more years than Herr Mtlnster- 

 berg; and yet with me there is a strongly pronounced error the other way. 

 It is the rightward-lying interval which to me seems longer than it really 

 is. Moreover, Herr M. wears concave spectacles, and looked through them 

 with his head fixed. May it not be that some of the errors were due to dis- 

 tortion of the retinal image, as the eye looked no longer through the centre 

 but through the margin of the glass? In short, with all the presumptions 

 which we have seen against muscular contraction being definitely felt as 

 length, I think that there may be explanations of Herr M.'s results which 

 have escaped even his sagacity ; and I call for a .suspension of judgment 

 until they shall have been confirmed by other observers. I do not my.self 

 doubt that our feeling of seen extent may be altered by concomitant mus- 

 cular feelings. In Chapter XVII (pp. 28-80) we saw many examples of 

 similar alterations, interferences with, or exaltations of, the sensory effect 

 of one nerve process by another. I do not see why currents from the 

 muscles or eyelids, coming in at the same time with a retinal impression, 

 might not make the latter seem bigger, in the same way that a greater in- 

 tensity in the retinal stimulation makes it seem bigger ; or in the way that 

 a greater extent of surface excited makes the color of the surface seem 

 stronger, or if it be a skin-surface, makes its heat seem greater ; or in the 

 way that the coldness of the dollar on the forehead (in Weber's old experi- 

 ments) made the dollar seem heavier. But this is a physiological way : and 



