♦ KNOWLEDGE ♦ 



[Sept. 11, 1885. 



OUR DUAL BR A IX. 



By Richard A. Proctor. 



IN a recent lecture at tlie Royal Institution, Mr. 

 Horsley offered evidence (which seems to me not 

 very strong) against the theory of the duality of the 

 juind. A person who, being already fairly well able to 

 draw with either hand separately, attempts to draw 

 simultaneously two different forms, however simple, with 

 both hands, is tolerably sure to fail. Mr. Horsley appears 

 to think that failure always results. When the effort is 

 made, he says, " There is a very definite sensation in the 

 mind of a conflict that is going on in the cortex of the 

 brain. The idea of the circle alternates with that of the 

 triangle, and the result of this confusion in the intellec- 

 .tual and sensorial portions of the brain is that both 

 motor areas, though remembering, as it were, the deter- 

 .mination of the experimenter to draw distinct figures, 

 jwoduce a like confused effect, namely, a circular triangle 

 and a triangular circle." 



Mr. Horsley adds that if the drawing is commenced 

 immediately at the sound of a signal (as should always 

 be done in such experiments), it will be found that the 

 triangle pr«iominates, while, on the other hand, if the 

 two figures are not commenced simultaneously, the one 

 last begun will ajipear most distinctly in the fused result, 

 in fact, will very markedly predominate. He reasons 

 upon this as follows : — " The idea of a triangle and circle 

 having been presented to the intellect of the sensory 

 centres, the voluntary effort to reproduce them is deter- 

 mined upon : now if we had a dual mind, and if each 

 hemisphere was capable of acting per se, then we should 

 have each intellectual area sending a message to its own 

 motor area, with the result that the two figures would 

 be distinct and cornet, not fused." 



To this experimental evidence and to its interpretation 

 t^vo distinct answers can be given. In the first place, it 

 does not always happen that the attempt to draw two 

 different objects simultaneously fails in the alleged 

 manner. Setting on one side as probably exaggerated 

 the story that Sir Edmund Landseer drew on one occasion 

 a deer's head with one hand, while he was drawuig a land- 

 scape with the other, I may cite from my own experience 

 a case which entirely invalidates Mr. Horsley's evidence, 

 lly friend. Professor Edwin Morse, of Salem, Mass., 

 could draw simultaneously, and that, too, before an 

 audience, two different objects with either hand. Or he 

 would draw [an object with one hand, and at the same 

 time write the names of the parts of the object with the 

 other. With practice much skill may be acquired in this 

 . !imbidextrous work. 



Here is a simple experiment to show the effect of 

 : practice. Try for the first time to write a word of 

 ; so many letters while you spell aloud, letter by letter, 

 another word containing the same number of letters. At 

 first you are almost sure (perhaps quite sure) to fail. 

 But after a few trials what had seemed impossible be- 

 comes feasible, and presently it becomes quite easy. 



Then, even if it were proved that we cannot do two 

 different things at once (apart from cases where either or 

 both is done automatically >, this would no more prove 

 that the brain is not dual than our inability to use the 

 two eyes simultaneously to do different work would prove 

 that ^Ye have not dual vision. 



As a mutter of fact we are able to prove very easily 

 thiit vision is double, by alternately closing and opening 

 cither eye. We cannot make any corresponding experi- 

 nient with the brain. We do nr t know even that, when 



1 ( nomena, 



the brain 



and even of 



in that each 

 iiililc to make 



we are trying to do simultaneuu^ly twn diff. niit tliiiit 



the two different sides of the br.iin :ii''- r-.Uiil inti. uctiii: 



We have positively no means of iliii i-miuinLr \\ licilur oi 



side, or the other side, or both m^I.- -f tli. iMaln .shall 1 



used, or of knowing whether tl . r. i, ■ 1. J-^ven i 



those cases where marked altiii ': i 



companied or preceded by m:irl. i 



show unmistakably that two dillirLiii j.ait 



may alternate in the regulation of action 



character, the person thus dually minded and charactered 



is perfectly powerless as to the particular mental side of 



him which shall come uppermost (or act alone). He 



often does not even know that he is passing or has passed 



from one state to the other. 



Since, however, we are absolutely c 

 eye does its work, while we are absi .Intel 

 them work separately yet simultaiitnu^ 

 eye work at long range, for examjilr, aiwl tin' other at 

 short range, the argument used by ill'. Ilnisli y in regard 

 to the brain is altogether without force. 



If any one could make his two eyes work separately, I 

 should be the one to do it, for my left eye is permanently 

 limited to work at short focal distances, while the right 

 eye has the usual range. Yet, not only am I powerless 

 to make my two eyes work separately and simultaneously, 

 but I am very seldom conscious of the fact that the left 

 eye is in reality presenting to the brain (so to speak) a 

 very different picture from that which is presented by the 

 right eye. 



I remained unconscious of the difference between the 

 focal lengths of my two eyes, marked though it is (inso- 

 much, that for ordinary distances my left eye is almost 

 blind), till I was about twenty ; at least I know it must 

 have been more than twenty-sis years ago that I detected 

 the peculiarity. I was in church one Sunday evening, 

 listening or not listening to a rather dreary sermon, in 

 which a person whom I had reason for regarding little 

 was enjoining duties which I had long learned to regard 

 a great deal; and being naturally inattentive to him, I 

 attended to other things. Now, there were in front of 

 me two bright lights, and I noticed to the right of them 

 two blurred lights, looking as large as the moon, where 

 assuredly no lights were. I looked at another group of 

 lights, three of them— and lo, to the right of them also, 

 a group of three,' similarly arranged, blurred lights. I 

 closed my left eye, and could see only the bright lights ; 

 I closed my right eye, and could see only the blurred 

 lights. That was all my left eye could do in the way of 

 showing those lights. 



Thus, for the first time in my life, I learned that so 

 far as distant objects were concerned I was almost blind 

 of one eye. But I soon found that my left eye was by 

 no means blind for near objects ; on the contrary, it was 

 and is very keen for them. Tet I cannot make my 

 eyes, different though they thus are, work separatel}-, 

 except in an imperfect sort of way, akin to the way in 

 which, in Mr. Horsley's experiment, one hand makes a 

 circular triangle while the other makes a triangular 

 circle. I am well assured my vision is double, as all 

 men are; nay, in my case vision is even of two kinds with 

 the two eyes : yet I have precisely the sort of evidence 

 respecting my two eyes which Mr. Horsley regards as 

 evidence of unity. 



Mr. Horsley cites a singular illustration of the duality 

 of the mind, of which, however, he endeavours to dis- 

 pose. The case is so remarkable, and, just now when all 

 sorts of foolish superstitions are as rife as ever, so in- 

 structive, that I give its details here prettj- nearly in full, 

 as recorded by Prof. Ball, of Paris. He "tells us that a 



