508 PSYCHOLOGY. 



wards from the paretic eye that this latter must turn 20° in order to 

 see it distinctly, the patient will feel as if he had moved it not only 20° 

 towards the side, but into its extreme lateral position, for the impulse 

 of innervation requisite for bringing it into view is a perfectly conscious 

 act, whilst the diminished state of contraction of the paretic muscle lies 

 for the present out of the ken of consciousness. The test proposed by 

 von Graefe, of localization by the sense of touch, serves to render evi- 

 dent the error which the jiatient now makes. If we direct him to touch 

 rapidly the object looked at, with the fore-finger of the hand of the same 

 side, the line through which the finger moves will not be the line of 

 sight directed 20° outward, but will approach more nearly to the ex- 

 treme possible outward line of vision. " 



A stone-cutter wdtli tlie external rectus of the left eye 

 paralyzed, will strike liis hand instead of his chisel with his 

 hammer, until experience has taught him wisdom. 



It appears as if here the judgment of direction covld only 

 arise from the excessive innervation of the rectus when the 

 object is looked at. All the afferent feelings must be iden- 

 tical with those experienced when the eye is sound and the 

 judgment is correct. The eyeball is rotated just 20° in the 

 one case as in the other, the image falls on the same part 

 of the retina, the pressures on the eyeball and the tensions 

 of the skin and conjunctiva are identical. There is only 

 one feeling wdiich can vary, and lead us to our mistake. 

 That feeling must be the effort which the will makes, mod- 

 erate in the one case, excessive in the other, but in both 

 cases an efferent feeling, pure and simple. 



Beautiful and clear as this reasoning seems to be, it is 

 based on a-n incomplete inventory of the afferent data. The 

 writers have all omitted to consider what is going on in the 

 other eye. This is kept covered during the experiments, to 

 prevent double images, and other complications. But if its 

 condition under these circumstances be examined, it will 

 be found to present changes wdiich must result in strong 

 afferent feelings. And the taking account of these feelings 

 demolishes in an instant all the conclusions which the au- 

 thors from whom I have quoted base uj^on their suj)posed 

 absence. This I will now proceed to show.* 



* Professor G. E. Miiller (Zur Grundlegung der Psychophysik (1878), 

 p. 318, was the first to explain the phenomenon after the manner advocated 



