876.. TKANSACTIOXS OF SECTION 1. 



Siuce then suVeral writor.s (Brodiiiaiin, Oskar uiul (Jecilie Vogt, VolscL, HftUi- 

 biutoii, and Mott) have 2>ublished accounts of the histological and physiological 

 localisation of the motor cortex in lemurs. There are so many discrepancies in 

 these various statements of fact and inference that we propose to describe the 

 results of our latest work, which thorouglily bears out the account given by Page 

 May in Cambridge four years ago; and we seize the opportunity to emphasise and 

 extend our views regarding the sigaificauce of these results. 



2. The Localisation of the Human Cerebral Cortex. 

 By Professor G. Elliot Smith, F.R.S. 



Two years ago I demonstrated to the An.atomical Society the ease, with 

 which one can map out the surface of the human cerebral cortex into a largo 

 number of areas, each of which presents distinctive features (thickness, colour, 

 arrangement and density of tlie iutracortical medullnry matter) which are appre- 

 ciable to the naked eye in fresh material, when cut with a scalpel. 



Last year 1 published charts of the human cerebrum showing the distribution 

 of these various anatomically distinct areas and indicating the causal relation- 

 ship existing between the situation of various sulci and the borders or the axes 

 of these areas. 



Shortly afterward Brodmann published similar maps, based upon the results of 

 the histological examination of the human brain. There is a remarkable agree- 

 ment between the two series of charts, which becomes more pronounced when it 

 is recalled that Drodmann represents one individual brain as seen flattened out in 

 a fresh condition, whereas I have shown the average condition of a large series, 

 represented on a specimen hardened in situ. 



Jiut even after eliminating these discrepancies and certain other differences 

 which a comparison of the tests (and not the diagrams only) of the two 

 memoirs will dissipate, there are still some points of disagreement between 

 ]?rodmann's results and mine. I have made a new investigation of all such points 

 of disagreement and, as the result, present new charts, modified in some 

 respects in accordance with Brodmann's results, but in others retaining my own 

 interpretation. 



Brodmann refuses to admit my interpretation of the meaning of the cerebral 

 sulci. But the examination of a large series of brains proves beyond any 

 possibility of error that the vast majority of the cerebral furrows are placed con- 

 stantly near to or actually at the boundary line between adjoining areas or, in 

 other cases, in the axis of a given territory ; in other words, the causal relation- 

 ship between the sulci and the distribution of the areas is patent. 



At the same time there is a considerable range of variation in the case of 

 certain sulci, especially the calcarine. Yet no furrow affords a more striking 

 demonstration of the varied factors which call a sulcus into being and determine 

 its form. 



3. 0)1 certain Features of Retinal Photo-electro Phe7iomena. 

 By Professor Francis Gotch, F.R.S, 



4. Colour-blindness and Colour-perception. 

 By F. W. Edridge-Green, M.D., F.R.C.S. 



The theory which T have advanced as an explanation of vision and colour- 

 vision is that light falling upon the eye causes the visual purple to be diffused 

 into the surrounding parts of the retina: that the cones of the retina are insensi- 

 tive to light but sensitive to chemical changes in the visual purple, which stimu- 

 lates the end of the cones and causes visual impulses. Then in the impulse itself 



