620 PSTCHOLOQT. 



sensations wliicli successively arise. It would seem indeed 

 that we fail of accuracy and certainty in our attainment of 

 the end whenever we are preoccupied with much ideal con- 

 sciousness of the means. We walk a beam the better the 

 less we think of the position of our feet upon it. We pitch 

 or catch, we shoot or chop the better the less tactile and 

 muscular (the less resident), and the more exclusively optical, 

 (the more remote) our consciousness is. Keep your eye on 

 the place aimed at, and your hand will fetch it ; think of 

 your hand, and you will very likely miss your aim. Dr. 

 Southard found that he could touch a spot with a pencil- 

 point more accurately with a visual than with a tactile 

 mental cue. In the former case he looked at a small 

 object and closed his eyes before trying to touch it. In 

 the latter case he placed it with closed eyes, and then after 

 removing his hand tried to touch it again. The average 

 error with touch (when the results were most favorable) 

 was 17.13 mm. With sight it was only 12.37 mm.*^ — All 

 these are plain results of introspection and observation. 

 By what neural machinery they are made possible we need 

 not, at this present stage, inquire. 



In Chapter XVIII we saw how enormously individuals 

 differ in respect to their mental imagery. In the type of 

 imagination called tactile by the French authors, it is prob- 

 able that the kinsesthetic ideas are more prominent than in 

 my account. We must not expect too great a uniformity 

 in individual accounts, nor wrangle overmuch as to which 

 one ' truly ' represents the process.f 



* Bowditch and Southard in Journal of Physiology, vol. in. No. 3. It 

 ■was found in these experiments that the maximum of accuracy was reached 

 when two seconds of time elapsed between locating the object by eye or 

 hand and starting to touch it. When the mark was located with one 

 hand, and the other hand had to touch it, the error was considerably 

 greater than when the same hand both located and touched it. 



f The same caution must be shown in discussing pathological cases. 

 There are remarkable discrepancies in the efEects of peripheral anaesthesia 

 upon the voluntary power. Such cases as I quoted in the text (p. 490) are 

 by no means the only type. In those cases the patients could move their 

 limbs accurately when the eyes were open, and inaccurately when they 

 were shut. In other cases, however, the anaesthetic patients cannot move 

 their limbs at all when the ej'es are shut. (For reports of two such cases see 

 Bastian in 'Brain,' Binet in Rev. Philos., xxv. 478.) M. Binet explains 



