March 20, 1S85.] 



♦ KNOWLEDGE 



229 



\^ AN ILLUSTRATED \.> 



MAGAZINE OF SCIENCE 

 PlainlyWoPvDed-Exactly Described 



LONDOX.- FEIDAY, J/.IA'C// 20, 1885. 



Contents op No. 177. 



Oar T»o Brains. By Richsrd A. 



Proctor 229 



The Voune Electricun. (lHut.) 



ByW. Slinso 230 



Plenstnt Hours with the Microscope. 



(;«:r..) Bv n. J. SUck '2.12 



Xieht Sicns lor March 233 



The PhilosjphT of Clothinj. IV. 



Bt W. Matlifu Williams 233 



Other Worlds than Ours 235 



Tricycles in ISSo. {lliut ) By 



John Browning 235 



Chats on Geometrical Measurement . 



(///«».) By B. A. Procter j 7 



PAOB 



The Inter-Oceanic Ship llailwar . 



(lUut.) :.. 239 



First Star Lessons, ( With Map.) 



Bv H. A. Proctor 2Ja 



Chapters on Modem Domestic Bco- 



nomr 211 



Editorial Gossip 2H 



Reviews 2\> 



Correspondence : Inscribed Uocks 



— Duality of Brain — The Tone of 



Controversy. &o 215 



Our Inventors' Column 24.S 



Our Chess Column 219 



I'ur Wbi^t Column 25(' 



OUR TWO BRAINS. 



Br Richard A. Proctor. 



SUGGESTIONS FOR THE PRACTICAL APPLICATION 

 OF THE THEORY. 



(Co)i<ini<e(Z frotn p. 194.) 



THE next point cited by Dr. Brown-Sequard does not 

 seem quite so clearly favourable to his views ; in fact, 

 it appears to me to sugyeM a rather strong argument against 

 the hope which he entertains that the general mental 

 powers may be improved by exercising both sides of the 

 brain in the same kind of work. He points out that very 

 few left-handtd persons have learned to write with the left 

 hand, and that those who can write with that hand do not 

 write nearly so well with it as with the right hand. 

 " Therefore," he says, " the left side of the brain, even in 

 persons who are kft-hauded naturally (so that the right 

 side of the brain controls the reasoning (acuities and their 

 expression) can be so educated that the right hand, which 

 that side of the brain controls, produces a better hand- 

 writing than that by the left hand, though this is controlled 

 by the better developed brain." This certainly seems to 

 show the possibility of training one side of the brain to 

 do a part of the work appertaining in the ordinary course 

 of things to the other ; but the ioferiority of the writing 

 with the left hand is rather an awkward result so far as 

 Brown-Sequard's hopes are concerned. For it looks very 

 much as though the habit of writing with the right hand, 

 which in the case of a left handed person is in fact the 

 wrong hand for writing vath, rendered the right brain less 

 fit to control that special department of its duties (for a 

 left-handed person) which relates to the expression of ideas 

 by writing. Now it may Vje a very useful thing to acquire 

 true duality of brainpower, if the ordinal ily less-used side 

 of the brain, for any particular action, does not acquire full 

 power for that function at the expense of the other side ; 

 but otherwise the advantage is not so obvious. If we could 

 train the left arm to be as skilful as the right, without 

 losing the skill of the right arm, we .should willingly 

 take the proper measures ; but merely to shift the skill 

 from one arm to the other would lead to no advantage, 

 even if we could be quite sure that it would involve no 



loss. And, as 1 have said, this piirtiriilar argument 

 .sui:g.=sts a test which can hardly be expected to favour 

 Biown-Scquard's theory. Left-handed jiersons are con- 

 timialiy cxoiciiing their left or less develupcd brain in 

 work ]iiopirly appertaining to the right brain (in tliis 

 case). Accordingly, with them the two lirains are more 

 equally ( .xtrcised than in the case of right handed itor- 

 sons. But arc the hit h iiulcd observed to be ordinarily 

 of better balanced mind than the right-liaudtd 1 Are they 

 less liable to paralysis of one side of the body, throu"li 

 having each brain readier to discharge the functions of the 

 olher / It seems to me that if neither of these relations 

 exists, and I can scarcely suppose that either could exist 

 without having long since been recognised, we may regard 

 Brown-Sequard's theories as interesting perhaps, and evt n 

 trustworthy, but we can scarcely ]ilace much reliance on 

 the hopes which lu; bases upon these theories. 



His next argument fcccms somewhat more to the 

 purpose. Right-sidedncss atTects the arms, as we know, 

 much more than the legs. It is presumable, therefore, 

 that there is not so .special a relation between the more 

 developed left braiu and the action of tho ri"ht leg 

 which is only the equal of the left leg, as there is 

 between the left brain and the more skilful of the two 

 arms. In other words, we may assume that both 

 brains control both legs. In fact, if, by etjualising the 

 practice of the two arms we are to bring the two brains 

 not only into more e(iual operation, but into combined 

 action on each arm, it would ajipear that the equal exercise 

 of the two legs ojKjlit tij have resulted in combining the 

 action of the two brains .so far as the control of the lower 

 limbs is concerned. So that we not only may "infer this 

 state of tho two brains from the observed powers of the 

 two legs," but unless we do assume this, the hopes enter- 

 tained by Brown-Sequard must be regarded as to some 

 degree negatived. Now, if the brains do thus act in com- 

 bination in controlling the lower limbs, it is clear that the 

 complete paralysis of a leg ought not to be so common as 

 the complete paralysis of an arm, for an arm would be 

 paralysed if only one side of the brain were aflected, but 

 for a leg to be ])aralysed both sides of the brain must be 

 aflTected. Dr. Brown-Sequard states that this is the case 

 at least to this degree, that " it is exceedingly rare that the 

 leg is aflected in the same degree by paralysis as the arm."* 



The hope entertained by Dr. Brown Secjuard is that by 

 teaching our children to use both sides of the body equally, 

 the two sides of the brain may be brought into more 

 uniform action. "If you have been convinced by the 

 arguments I have given that we have two brains," he says, 

 " it is clear that we ought to develop both of them, and I 

 can say at any rate as much as this, there is a chance — J 

 could not say more, but at least there is a chance — that if 

 we develop the movements of the two sides of the body, 

 the two arms and the two legs, one just as much as the 

 other, the two sides of the brain will then be developed 

 one as much as the other as respects the mental 

 faculties also." There is a connection between the develop- 

 ment of the brain as regards the mental faculties and the 

 development as regards leading movements on one side of 

 the body. Therefore, Brown-Sequard considers that, if we 

 train the left side of the body as carefully as we are in the 

 habit of training the right, there is a chance that we should 

 have two brains as respects mental functions instead of one, 



* I do not feel quite snra th.-it I have rightly dealt with Dr. 

 Brown-Sequard's argument in thig case; because he has presented 

 it very brieflj-, with the remark that it cannot be understood well 

 except by medical men, and my explanation, not requirinf; a 

 medical training on the reader's part, ia tlierefore presumably 

 inexact. 



