398 



SCIENCE. 



[Vol. VIII., No. 195 



it is a little curious to see, that, while the great 

 ship is certainly going to the bottom, the small 

 torpedo-boat itself floats apparently uninjured. 



LOCALIZATION OF FUNCTION IN THE 

 CORTEX OF THE BRAIN. 



A CONVENIENT Summary of the main points 

 that have been established by experiments on 

 animals, by pathological records and anatomical 

 research, regarding the relation of certain parts of 

 the braiu to the various senses and systems of 

 muscles, is a very welcome contribution to this 

 vexed question. If, in addition, the work brings 

 new light on some of the problems, and a worthy 

 appreciation of its predecessors, it is doubly 

 welcome. The recent work of Dr. Luciani and 

 Dr. Seppilli has these claims to our highest praise. 



The view of Flourens, that all the parts of the 

 brain were functionally equivalent, was followed, 

 after the discovery of the excitability of the cortex 

 in 1870, by the very opposite view that the brain 

 consisted of a collection of areas definitely cir- 

 cumscribed, each of which had exclusive charge 

 of a certain function. The view held by our 

 authors, agreeing with that of Exner, Goltz, and 

 others, is a mean between the two. The different 

 parts of the cortex have very different relations 

 to the several functions. But a centre is not a 

 definitely limited area : it has a focus and a 

 'periphery,' but no hard and fast boundary-lines. 

 The peripheries of the various centres overlap. 

 Take the usual centre, for example. If you regard 

 the sight-centre as all that part of the cortex the 

 removal of which will cause disturbances of vision, 

 then this centre is almost too extended to be local- 

 ized at all ; but, if you distinguish between tran- 

 sitory and permanent (though gradually decreas- 

 ing) impairment of vision, the occipital lobe, with 

 a small part of the adjoining parietal, is at once 

 marked as the focus of the sight-centre : its 

 ' periphery ' extends in the direction of the frontal 

 and temporal lobes. An injury to the peripheral 

 portions will cause less severe and less permanent 

 impairment of vision than injury to the focus. 



The extensive destruction of one occipital lobe 

 produces blindness in a small external segment of 

 the retina on the same side, and in a large internal 

 segment of the retina on the opposite side ; i.e., 

 each centre is connected with both sides of the 

 body, but more with the opposite side. This 

 furnishes a simple scheme of the decussation of 

 fibres in^the optic chiasma. The general results 



Die functions-localisation auf der grosshirnrinde an 



thierexperimenten und klinischen fallen nachgewiesen. Von 



' Dr. LuiGi Luciani und Dr. Giuseppe Shppilli. Autorisirte 



deutsche ausgabe von Dr. M. O. Fraenkel. Lepzie, Denicke 



1886. 8°. . o , 



are compactly represented in a diagram of the 

 dog's brain, in which the size and proximity of 

 the dots show the ' intensity ' of the different parts 

 of the centre, while the shaded dots show the pro- 

 portion of the centre connected with the same 

 side of the body. 



The accompanying diagram of the dog's brain 

 shows the location and extent of the visual centres, 

 as proved by the impairment of vision due to ex- 

 tirpation of this area. The occipital region, as 

 indicated by the size and frequency of the dots, is 

 most immediately connected with this function ; 

 but an area of minor intensity extends towards 

 the frontal and parietal lobes. The shaded dots 

 indicate (roughly) the part (a smaller one) of the 

 centre connected with the retina of the same side ; 

 the others, the part (a larger one) connected with 

 the opposite retina. 



The centre for hearing has likewise a focus and 

 a periphery, and the scheme of decussation would 

 be quite the same. The focus is in the temporal 

 lobe, with the periphery extending in the direc- 

 tion of the parietal and frontal lobes, of the hip- 

 pocampus and cornu ammonis. The attempts at 

 localizing the centres for smell and taste are less 

 definite and less certain. 



On the pathological side, the correlation of 

 certain disorders with lesions of certain parts of 

 the brain tends to the same results in the main, 

 and thus makes the experimental evidence doubly 

 important. 



The central convolutions and the immediately 

 adjoining parts of the parietal and frontal convo- 

 lutions form the sensor-motor zone. It is the 

 terminal station for the reception of skin and 

 muscle impressions, as well as the origin of the 

 voluntary control over certain muscles. The 

 motor zone is directly excitable by electrical stimu- 

 lation, and is the part the irritation of which pro- 

 duces epileptic spasms. A study of the order in m 

 which these spasms affect different groups of 1 

 muscles, with a post-mortem examination of the 

 brain, tends to a more definite localization of the 

 facial centre, the arm-centre, and the leg-centre. 

 The chapter on epUepsy, from the point of view 

 of Hughlings-Jackson, is a valuable presentation 

 of the subject. 



