128 



confusion. One must begin by acknowledging a stratum of 

 texture on the surface of the convolution diiferent from the 

 main bulk of grey matter ; then the pale band or couple of 

 bands which are seen with the naked eye dividing the grey 

 substance into other strata attract attention ; and when both 

 bands are present an obvious division into at least six layers 

 is obtained. But the question at once occurs — Do the pale 

 bands separate utterly distinct strata from one another, or is 

 it not rather the case that while the grey matter undergoes 

 changes of composition as it recedes from the surface, it is 

 traversed by other structures at a varying level ? As regards 

 the deeper pale band the second explanation is probably 

 true; its existence as a special stratum appears to be due 

 very much to the separation of a series of horizontal fibres 

 from a much larger tract of them which is immediately in- 

 ternal to the grey matter. The other light coloured stratum, 

 which we may term the primary pale hand, and of which I 

 can speak more confidently as being more than an accumula- 

 tion of transverse fibres, maintains a sufiiciently definite 

 position as related to the surface, but the strata which it 

 separates are neither so unconnected nor of so different a kind 

 as to give importance to KoUiker distinction of the " pure 

 grey" and " yellowish red." 



Arndt divides the first or outermost layer of Kolliker into 

 two, a fibrous layer and a granular, with sparsely strewn, 

 small, irregular nuclei, and delicate fibres taking all direc- 

 tions. His third layer, consisting of substance rich in nuclei 

 which require a high power to show that they belong to nerve 

 corpuscles with their chief poles not all pointed in one direc- 

 tion, combines Avith his fourth, which is characterised by 

 jDjramidal nerve corpuscles pointing to the surface, but still 

 not much larger than the nuclei, to correspond (according 

 to him) with the pure grey layer of Kolliker, and is sepa- 

 rated by horizontal fibres, which he takes for the primary 

 pale band, from the deeper part of the grey matter. This 

 remaining part he calls at first the fifth layer, but subsequently 

 divides into fifth, sixth, and seventh layers, to accord with 

 Meinert; it contains pyramidal corpuscles of large size, 

 especially in its more superficial portions. It is very no- 

 ticeable, however, that in Arndt's figure of a vertical section 

 through the different layers the strongest indications of 

 horizontal fibres are represented in such a position that 

 they would separate the largest nerve-corpuscles into two 

 layers. This I have no hesitation in considering the true 

 position of the primary pale band ; but, undoubtedly, hori- 

 zontal fibres exist much more superficially, and they may 



