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Tribune Extras Lecture and Letter Scries. 



were the other side of tho brain which produced that 

 complete paralysis, if we found that paralysis is more 

 or loss extensive, more or less durable according to the 

 extent of the disease in one-hull of tho lirain, then wo 

 might conchiile that tho disease has destroyed the 

 power of will in that halt' of the brain, and 

 thereby produced the loss of voluntary move- 

 ment on tho opposite side. But u is not 

 what we see. We see that the lesion which has destroyed 

 one half of the brain may allow voluntary movement, 

 but a lesion which is not larger than a poo- in any one 

 part of the brain can produce a loss of voluntary move- 

 ment. Therefore we are to admit that when the 

 paralysis of movement comos In connection witli disease 

 of one half of the) brain, it depend* on an influence 

 starting from the place where the disease is acting upon 

 remote parts so as to produce a cessation of activity 

 there, and a paralysis therefore. 



SKAT OF THE FACULTY" OF SENSATION. 

 There is the same reasoning to bo made as regards 

 perception of sensation. There also we find the same 

 tiling. I shall not insist on that point therefore. We 

 know a thousand cases of disease occupying 1 one-half of 

 tho lirain that has not produced the slightest alteration 

 in the power of feeling. But, if it is so ic remains to be 

 explained how it is, however, that the two halves of the 

 brain come to bo somewhat different, and that the 

 physiological and pathological study .of the two halves 

 of the brain indicates great differences in that respect. 

 If wo pass in review what is known, wo find very great 

 differences indeed. Those differences depend on the 

 fact that through the fault of our fathers and 

 mothers, the faults that weigh upon us and have led us 

 to make use of only one-half of our body for certain acts, 

 and one-half of our brain for certain other aces also wo 

 find that it is owing to that defect iu our education that 

 one-halt of our brain is developed for certain things, 

 while the other half or the brain is developad for otner 

 things. As regards what belongs to tho lefD side of the 

 brain compared with tho right side of the brain, allow 

 me to say tuo most important feature iu its physiology 

 or pathology is what a French physician 

 has discovered. It is, as I have said 

 already, that to that side of the brain belongs 

 the faculty of expressing ideas by speech. Basides, that 

 mental lacultf of speech the left side of the braiu pos- 

 sesses iu a much more marked degree than the right the 

 power of moving the tongue and larynx and muscles of 

 the chest to produce the sounds of articulate voice. Ar- 

 ticulation of sounds in speech in a great measure de- 

 pends on the left side of the brain. I mean by tho words 

 "in a great measure" that it is chiefly tue left side of 

 the bruin which has the power of actiug upon those, or- 

 gans. So tli tt more frequently in cases of disease of the 

 loft si le of the braiu ao we find tho difficulty iu tho 

 mechanical part of the speech than iu cases of disease of 

 tho right side of tho braiu. But that, although mechan- 

 ical, is .something lilco a gesture. There is a mental si-n 

 in it. and although it is a mechanical thing in it>lf, I 

 cannot bui. consider it as representing SOLUO mcutal 

 trouble. 



MEMORY. NOT MUSCULAR POWER, LOST. 

 My pupil and assistant in London, who ha* In roine a 

 Very eminent man since, Dr. Howling Jackson, has also 



insisted on tnat point, that it i. tin- mory of direction 



of movements ot tiio muscles which serve to articulate, 

 which Is l<>st, and not the mere power of moving tho 

 muscles of the tongue, larynx, or cuust. I have h 1.1 m-oof 

 Of itiu a great many instances, that, when toll to do so. 



the patient could move the tongue in any direction, 

 could move the larynx and utter sounds very well, but 

 could not articulate, so that it was the mental 

 part of that mechanical act the mental pjrt 

 of which was altered, and not purely a 

 mechanical action lost. The left side of the brain is 

 also the one that loads in gestures, and that by a very 

 simple reason, which is, that it is tho left side of tho 

 brain which leads chiefly the movement of the right 

 arm, and it is chiefly with tho right arm that wo make 

 our gestures. Still, it is likely, as pathological facts 

 show, or at least appear to show, that even tho motion 

 of tho left arm depends on the left si le of the brain as 

 regards gestures, as we flud that in p.itiants who have a 

 disease of the right side of the braiu tho faculty is lost 

 of making gestures with either tbe right or the left arm. 

 That of course, shows, or at any rate seems to show, that 

 the left side of tho brain is the organ for gestures chiefly. 

 In a few cases, however, of dis-a-iof the right side of 

 the brain, tho power of making gestures has been lost as 

 well as in case of disease of the left side of that organ. 



As regards the power of writing, there is a difficulty 

 there, as you will early understand. Still there 

 are many facts which show that tho power of 

 writing can be lost more easily, and is lost more fre- 

 quently in cases of disease of the left side of tho brain 

 than in cases of disease of the right side of the brain a 

 difficulty which many of you have understood without 

 my mentioning it. Wo conclude that the right arm is 

 not rarely paralyzed in diseases of the left side of the 

 brain, and as wo write with the right arm, it is very 

 natural that, on being paralvzod, we cannot write; but 

 very few patients have lost altogether the movements 

 of the fingers, and cannot form tho least sign, though 

 many of them cannot at all form a letter. They will be 

 able, however, if they have a letter written by some one 

 whose handwriting is not very much different from 

 theirs (and sometimes when it is diUVruut), they will be 

 ahle to imitate what is under their eye, but they cannot 

 from memory write anything; at all events, thoy cannot 

 express ideas by writing. They are attacked with what 

 is called the agraphia that is. a loss of the faculty of 

 expressing ideas by writing. Ij many of these cases of 

 patients attacked with agraphia. there is a perfect power 

 of moving the right arm. Tuo arm is not paralyzed in 

 cases where tho left side of the brain is paralysed; ihere 

 is no paralysis on the right side of the body or tue loft ; 

 no paralysis anywhere. In those cases, it lias occurred 

 sometimes that the patient could not writ:- at all ; so 

 that it is clear that tho loss of the faculty of expressing 

 ideas by writing does not depand on the paralysis which 

 in these cases had no existence. 



INTELLECT MOST DEPENDENT ON THE LEFT SIDE 

 OF THE BHAI.N. 



Another thing depends on disease of the left side of 

 the brain more than tho right side of the brain, and that 

 Is intelligence. Alterations of the mind inamtestnig 

 themselves in tho various forms of insanity depend more 

 frequently, I should say, on diseases of t!ie left side of 

 the brain than on diseases of the right side. This is all 

 I know now which belongs to the loft si le of i ho brain. 

 Tho right sido of the brain is quite different. From ul! 

 that I hive stated about the loft side, as you will see, 

 that organ is chiefly tho organ serving the mental facul- 

 ties, either iu speech, or in intelligence, or in gesture, or 

 n writing. That organ, therefore, is tho 

 mportant organ in our system adapted 

 ;o the life of communication between ourselves and our 

 irctbreu In a mental way. But tho other organ tho 

 right sido of tho braiu, in some individuals, as you will 



