n 



MATURE 



\Nov. 23, 1876 



increasingly popular but thoroughly unphysiological con- 

 ception of Localisation. Were not the current notions 

 respecting organ and function very chaotic, and were not 

 the indispensable artifice of analysis mistaken for more 

 than an artifice which demanded rectification by synthesis, 

 we should marvel to witness so many eminent investi- 

 gators cheering each other on in the wild-goose chase of 

 a function localised in a cerebral convolution, I will not, 

 however, dwell on this point here, because it is one which 

 would require a long discussion. It is only mentioned as 

 a general caveat, and as leading up to the main question 

 of cerebral excitation. 



In 1870 Hitzig and Fritsch startled the scientific world 

 by announcing that the universally accredited notion of 

 the brain not being excitable was an error. The most 

 eminent experimenters had declared that mechanical, 

 chemical, and electrical stimuli were utterly powerless to 

 excite the grey matter ; and many a writer pointed to the 

 paradox of the chief organ of sensation being insejisible. 

 We may here note another example of the common con- 

 fusion of sensibility with pain ; the brain was said to be 

 " insensible " because no cutting, burning, pricking, or 

 galvanising of it yielded evidence of pain ; whether other 

 evidence of sensibility might have been present was not 

 asked. The utmost the experiments could prove was that 

 the brain was not excitable by these abnormal means, 

 though excitable by the very different normal means of 

 peripheral stimulus. And even this conclusion Hitzig 

 and Fritsch upset, by demonstrating that there were cer- 

 tain regions of the cortical substance which were excit- 

 able by electricity, as proved by the movements following 

 such excitation ; and the other " non-excitable regions " 

 they inferred to be also excitable, though in another way, 

 namely, by the production of sensations {Vorstellungen). 



This was an epoch-making discovery. Experimenters 

 in Germany, Italy, England, Switzerland, France, and 

 America, quickly verified it, although differing among each 

 other both as to the particular facts, and their interpreta- 

 tion. Among these followers the chief place must be 

 assigned to Dr. Ferrier, both for the extent and the pre- 

 cision of his results ; accordingly the names of Hitzig and 

 Ferrier are usually coupled in speaking of the new hypo- 

 thesis that various motor centres are located in particu- 

 lar spots of the cerebral cortex. 



Although I have called it an epoch-making discovery, 

 because I believe it will open a new track for the ana- 

 tomical and physiological interpretation of the nervous 

 mechanism, which will one day enable us to follow the 

 whole pathway of stimulation, instead of — as at present — 

 leaving us with the vague conception that " somehow " 

 the cerebrum determines movements by setting the motor 

 apparatus in action, I do not think that the hypothesis 

 of motor centres in the cerebrum is tenable ; nay, more, 

 I do not think that Hitzig and Ferrier have proved the 

 grey substance to be excitable. It is one thing to admit 

 that the brain is excitable, another to admit that the 

 excitation so effected is effected by calling into activity 

 the special property of the grey substance. We do not 

 consider the fauces to be the centre of vomiting, although 

 tickling the fauces will be followed by retching. We do 

 not consider the centre of laughter to be located in the 

 sole of the foot, because tickling the sole causes laughter. 

 Something more is needed ; and it is preciseli'this ome- 



thing more which the Hitzig-Ferrier hypothesis has yet 

 to find, namely, the anatomical connection of the so-called 

 centre with the motor apparatus. 



Has any proof been adduced that the electrical stimulus 

 first acts on the cortex, and then — by the stimulation 

 there produced — on the white substance, which in turn 

 acts on the motor ganglia ? N^one that withstands criti- 

 cism. Knowing as we do that if the cortex be removed, 

 or destroyed, the electrical stimulus nevertheless on reach- 

 ing the white substance determines the same movements 

 which had previously been determined when the stimulus 

 was applied to the cortex, we may fairly ask : What proof 

 is there that the current does not pass through the cortex 

 (as through any other conducting medium) without exciting 

 its activity ? That it does simply pass through the cortex 

 is probable on two grounds : (i) only the electrical current 

 causes an excitation ; mechanical and chemical stimuli 

 have no such effects, because they cannot pass through 

 the cortex to reach the white substance ; (2) it is a well- 

 known law that the propagation of neurility, imlike that 

 of electricity, takes place only at insensible distances : if 

 the nerve be divided, and the two cut surfaces be brought 

 into the closest possible contact, there is still no propaga- 

 tion of the excitation from one surface to the other ; 

 whereas electricity passes freely across the cut surfaces. 

 Now here Dr. Burdon Sanderson's decisive experiment, 

 formerly referred to, comes, as I said, to cut the very 

 ground from under the Hitzig-Ferrier hypothesis. " If 

 that part of the surface of the hemisphere which comprises 

 the active spots is severed from the deeper parts by a 

 nearly horizontal incision made with a thin-bladed knife, 

 and the instrument is at once withdrawn without disloca- 

 tion of the severed part, and the excitation of the active 

 spots thereupon repeated, the result is the same as when 

 the surf ace of the uninjured organ is acted itp07t " {Proceed- 

 ings of the Royal Society, No. 153). Here the interruption 

 caused by the incision, while it must have completely pre- 

 vented the propagation of neural excitation, did not 

 prevent the propagation of the electrical current. Clearly 

 therefore the simple passage through the cortex v.'ill 

 explain all the effects of electrical stimulation. Clearly 

 therefore some other proof is needed before we can assign 

 the motor effects to an excitation of the cortex. The 

 arguments of Dr. Ferrier (pp. 135-6) are all set at nought 

 by Dr. Sanderson's experiment ; and on the physiological 

 and histological views now adopted I do not see how Dr. 

 Sanderson's experiment can be brought into agreement 

 with the motor centre hypothesis. 



Nevertheless, although I say that the preliminary fact 

 of excitation of the cortex is not proved by Hitzig and 

 Ferrier, I do not myself doubt that fact, although my 

 reasons will sound so paradoxical that I must wait for 

 another article to give them expression. 



George Henry Lewes 

 {To be continued.) 



GREEK AND LATIN PHILOLOGY 

 Baur's Philological Introduciioji to Greek and Latin for 

 Stude7its. Translated from the German by C. Kegan 

 Paul and E. D. Stone. (London : King and Co., 1876.) 



WITH the publication of Jacob Grimm's " German 

 Grammar " the comparative study of language 

 entered upon a new period of existence. Bopp and the 



