3. The tftitdf/ of the Cortes L'erebrl in the Normal State. 



xv 



\Vo come next to the study of the cortex cerebri in the normal state. This constitutes 

 the basis of the present research and is so important that it may be regarded as the 

 corner stone in the histological foundation upon which the superstructure of cerebral 

 localisation may be reared by workers in other departments. Of the cortical components, 

 two, the nerve fibres and the nerve cells, act as bases for investigation, and the topical 

 variations exhibited by these elements serve as certain guides to the creation of a sub- 

 divisional map of the brain surface. As to the nerve fibres, it has been known for some years 

 that these are subject to variations in size, arrangement and number or wealth in different 

 situations; but, up to the present, advantage has not been taken of these variations in 

 making a careful and comprehensive survey of the surface, with the end expressly and 

 constantly in view of endeavouring to ascertain whether or not fields having established con- 

 nections with different physiological functions are characterised by the possession of some 

 specific fibre arrangement, which will render their correct delineation possible. I am hoping 

 that proof of the unvarying exercise of this fundamental aim will heighten interest in, and 

 add to the appreciation of my individual labours, for I feel that I shall be able to show 

 that most valuable and significant results are obtainable in this manner, and I will also 

 venture the opinion, that others who have applied themselves with undeniable industry to 

 a histological study of these fibres have failed to elicit information bearing on the localisation 

 of function, solely because their methods have been uninfluenced and undirected by the 

 above-mentioned fundamental principle. Similar remarks apply, but not so forcibly, concerning 

 the second cortical constituent, the nerve cell. Starting from the year 1872, when Meynert's 

 classical research saw light, the literature has been enriched by a steady and constant 

 stream of observations dealing with variations in the architectural as well as the intimate 

 structure of these highly important elements. But with rare exceptions these observations 

 have been founded on what may be called piecemeal work, at the most two functional areas, 

 the motor 1 and the visuo-sensory, can be pointed to as having had their boundaries accurately 

 delineated by cytological methods, and it is plain that observers have previously baulked 

 an attempt to explore the whole surface in a comprehensive and complete manner on 

 account of the magnitude of the task. To the accomplishment of this undertaking I now 

 lay claim ; and its independent value is materially enhanced by the fact that it has enabled 

 me to make a collateral comparison of cell lamination and fibre arrangement in section 

 after section and millimetre by millimetre over the entire surface of the human cerebrum 2 . 

 Indeed, not only has this been clone in the case of the human subject but an identical 

 plan of research has been extended to the brains of those members of the ape family 

 which come second to man in the scale of phylogeny, and this branch of the research, 

 which may be included under the heading of normal histology, can also be proved to be 

 productive of gain. Before leaving this subject reference may be made to two other 

 cortical components about which our knowledge is scanty at present but which may in 

 the future serve as checks to perfect localisation ; of these, the first is what is commonly 

 known by the term neuroglia, and it is conceivable that this exhibits morphological, 

 numerical, developmental, and possibly functional variations in differHt areas, in the same 



1 The motor area was virtually defined by Bevan Lewis and Henry Clarke iu 1879 (ride chapter on motor area). 



2 In more than one case I have converted an entire cerebral hemisphere into serial sections and alternately 

 stained these for the display of nerve cells and nerve fibres. 



