Oct. 2, 1885.] 



KNOWLEDGE 



ing portion in the opposite half or hemisphere ; in fact, 

 that structurally, and in part functionally, the excito- 

 motor areas should be regarded as dual. I then showed 

 that duality of mental function in the highest sense, i.e., 

 the simultaneous correct performance of two totally 

 dificrent voluntary acts, was impossible provided that 

 such correct performance necessitated the concentration 

 of the attention on each subject. 



You quote the case of Prof. Morse, who " could draw 



simiiltaneously two different objects with 



either hand," as invalidating my argument, since such an 

 act would suggest the possibility of the two (highest) 

 cortical - motor areas functionalising at once. Now a 

 good many people, myself included, can perform this 

 feat ; but in every instance where I have carefully 

 examined the performance I find that the two pictures 

 are not drawn "simultaneously," in the strictly accurate 

 language of scientific experiment — that there is always a 

 fraction of a second's interval in time between the move- 

 ments of the hands when these dittV-r at all. We know, 

 further, that -2 of a second is sullicient interval of time 

 to allow of alternation in the efferent discharge from the 

 two halves of the brain, while I need scarcely add that 

 the ordinary bystander does not appreciate so small an 

 interval of time. As you say truly, it is possible to 

 practise synchronism in actions, and the old schoolboy 

 trick of slapping horizontally the chest with one hand 

 while the other is rubbed up and down is a familiar 

 example of the fact; but this very word "practice" 

 introduces us at once into an absolutely different field of 

 phenomena to those I dealt with in my lecture. It means 

 that an action, at first voluntary, becomes automatic, or, 

 as we should more correctly say, it belongs to a lower 

 grade of simpler, because more often repeated, reflex 

 actions in which the attention is scarcely, if at all, 

 required for their correct performance. 



My experiments and statements refer solely to the 

 investigation of purely voluntary phenomena, in which 

 the attention had to be fully concentrated on each 

 problem that was brought before it. 



I found, as the result of a large number of experiments 

 (some hundred.s) performed bj- other people as well as 

 myself, that two such efforts of volition could not be 

 Jierformod correctly at absolutely the .^;ime moment of 

 time, and the test I r.r. A I u^y■■\\. :^.■^ ■..{•^v I..;,-- 

 continued attempts, ih ly 



"practice." May I In : :; i - :■ 



Morse was started li\ ,i -1^ 



ircle and i 



'gl^'. 



his f^ ' .-lues within the domain of exact 



scieniiih > \,,. ; '.;■... :,i. 



Further, yi.u .,a_\ that we " do not know that when we 

 are trying to do simultaneously two different things, the 

 two different sides of the brain are called into action." 

 Permit me to say on this point tliat wc actually do know 

 (from clinical evidence, some of which 1 i|uott(l in mv 

 lecture) that the fii'o halv, . of tlic In-:, in iut .o,;!-. .1 ili 

 such actions as my o.\|-oiiinciit invoKo, ai,<l \sr now 

 know the parts conccrncil as \\A\ as wc do tlic niaclilncrv 

 of the circulation of tlu' Mood. 



Passin^^' fiMiii ihis pari of your article to the question 

 of the evidence \\eileii\e from our visual apparatus, I 

 am afr.iid 1 scarcely fulluw you in your remarks about 

 " working the eyes " as iinalogous to working our hands, 

 for we have, of course, absolutely no voluntary power over 

 our eyes {e.g., in focussing them, itc). But if I under- 

 stand you rightly, you would further seek to show that 

 your mind must be dual, because it geta simultaneously 

 two different messages from your eyes, owing to 



their focal distances being different.* This very 

 fact of peo))Ie seeing perfectly well with one de- 

 fective eye for so many years without discovering 

 any difference is a fact strongly in support of my views, 

 for it is well known that the (single) mind ignores the 

 false evidence from the defective eye. The " double 

 vision," as you call it, of every person is a splendid 

 example of the unity of function in the nervous system 

 while the apparatus is duplex in structure. We normally 

 only get one idea from our two eyes — we cannot con- 

 centrate our gaze on two objects at once, however hard 

 we try, consequently the attention is never concerned 

 with more than one thing at a time. Further, we now 

 know (from clinical evidence) that, although there ifl 

 a sight centre in each half of the brain, each is 

 educated simply as its fellow, and therefore if one is 

 destroyed the person knows what he sees just as well 

 as before, showing clearly that although the apparatus 

 is double its function is single. The case of Prof. Ball 

 similarly shows clearly that the brain is dual, that under 

 certain circumstances of disease one sensory perceptive 

 area may be irritated, the other remaining at rest. Such 

 a patient will, therefore, imagine he hears voices talking 

 to him, and he will answer and act accordingly, but the 

 conversation, Ac, is alternate — there is no double mental 

 action here, any more than when two persons talk alter- 

 nately to one another. 



I greatly regret that the necessities of a lecture pre- 

 vented my elaborating my argument, or, perhaps, you 

 would have seen that I am reaUy in perfect agreement 

 with yourself in regarding the brain as a dual machine, 

 my only contention being that in a purelij cohmtary act 

 its function is single. 



SURGERY FOR PIANOFORTE 

 PLAYERS. 



rpHE most earnest advocates admit that evolution 

 J. is an extremely slow process : that it produces 

 wonderful results, but that its operations occupy a 

 corresponding amount of time. Certain it is, that the 

 process is not keeping pace with the requirements of 

 modern times, and that the artificial development of the 

 human faculties has of late taken p-eeclcnce over the 

 natural results of time. 



llclmholtz, after makim,' an cxl,au>iive study of the 

 human eye, declared that slu ukl he receive an optical 

 instrument of man's makiuu' which contained so many 

 defects as the eve, he should be justified in returning it 

 to the m.annf:ictuvers. But it is tlusc very defects 

 which luivc stiiiiulatea lua:.'- ii „■ n i ;n to hud a remedy. 

 So eonipleielN has tlu .; .f ; ' !■ s come to his 



assistance that, with the i . ; , f s . n- in microscope 

 and tele^eoI,e. lie is [lexv. ^ . • I ■ !' ' _ !: eajuble at once 



svsteni. Vet no pro-re.>, exee| i, |erii,.l>, u'l the_power 



of discri 





■ 1 '•' 



■a[v 



hi Id is probably 

 to that of his 



In other directions, however, man may be improving. 

 His hands, from their constant use of sensitive instru,- 



* Not quite this. I used double vision only as au iUustrntim of 

 brain action j not as an example of it. I certainly did not suppose ■ 

 it was a different mind which recessed the imperfect images given 

 by the shortsighted eye.— R. P. . - . • 



