106 G. STANLEY HALL AND E. M. HAKTWELL. and of ocular judgments of relative distances of movable pins, corresponding to A. III., were made, but not enough to warrant conclusions as yet, in the complex cases of B. C. I. Two large thimbles were made for the two index fingers, one of which carried a light board fifteen centimetres square, to the plane of which the finger, when inserted in the thimble, was perpendicular, while the other thimble was weighted to equal the weight of the first, plus the board. Upon this latter was fastened a piece of heavy paper, with concentric circles, one centimetre apart, printed on it, the common centre being adjusted to exactly coincide with the position of a short needle on the end of the other thimble, so that if the index fingers, thus armed, were brought accurately together, the needle of one thimble would pierce the paper on the board carried by the other exactly in the middle ; 1 the paper being of course removable, when the holes became too numerous to be accurately counted or located. This experiment was made with closed eyes, both arms being moved systematically from the shoulder. Be- sides this first movement just described, two other series of records were made, both by approximating the arms to the median plane by symmetrical shoulder- movements, in the one case directly over the head (II.), and in the other low down behind the back (III.). In each case effort was made to bring the index fingers, armed with recording apparatus, as accurately together as possible, with an impact strong enough to leave a trace, but at the same time so gently that, even if there was con- siderable error, the direction could not be inferred from the lever- age of the recording table, for in that case it would be instinctively corrected at the subsequent movement. In observing the record thus made, it was found first that the points of the pins were by no means accurately in the centre of the concentric circles, like shots about the bull's eye of a well-used target, but about another and often rather remote centre, the position of which, best esti- mated by simple inspection, is comparatively constant for the same person. One extremely right-handed and one extremely left-handed person brought the preferred hand constantly farther from the axis of rotation at the shoulder in each of the three positions than the non-preferred hand, as if the preferred arm were slightly longer, and experience had not taught the proper compensation. Another strongly right-handed man brought the left finger farther front in II., farther back in III., with no dis- cernable difference of elevation in II. The preferred hand w<is 1 The apparatus here described, and that used in A. were both devised by Professor H. P. Bowditch of the Harvard Medical School, with whom these experiments were originally begun. The paper described above is the same as that used by Bowditch and Southard. See their article en- titled " A Comparison of Sight and Touch," in Journal of Physiology, Vol. iii., No 3, Plate xvii.
