129 



possibly sometimes form a slight indication of a pale band 

 superficial to the primary one. 



Lockhart Clarke, in his paper in 1863, enumerates eight 

 layers, but in his more recent account he combines in one 

 his first or fibrous, and his second or nuclear layer. His 

 first layer as altered corresponds with the first, second, and, 

 at least, ])art of the third layer of Arndt ; his third and fifth 

 are the pale bands ; the sixth is the deepest part of the grey 

 matter ; and he terms the white centre of the convolution a 

 seventh layer. 



The superficial layer of nerve-fibres immediately beneath 

 the pia mater apjDcars to have been best described by 

 Remak, who recognised that it was not evenly distributed 

 over the surface, but Avas less developed on the vertex than 

 on the base. It consists in great part of medullated fibres of 

 different sizes, running horizontally on the surface of the brain. 



That beneath this superficial network of medullated fibres 

 there may be sometimes present a sparsely nucleated layer of 

 tissue, as is described by Arndt as constituting what he calls 

 the second layer, I am not disposed to deny, although it is 

 noteworthy that both Lockhart Clarke and Meinert throw 

 the tissues which constitute Arndt's first two layers into one 

 layer ; but I am satisfied that both the network of medul- 

 lated fibres and whatever sparsely nucleated tissue may 

 be sometimes below it, are in some places absent, and that 

 then there is in contact with the pia mater a very densely 

 nucleated layer. 



This densely nucleated layer may be termed appropriately 

 enough the external layer of nucleated protoplasm. Its 

 nuclei, rounded in form, are most densely crowded in its 

 most superficial part ; while, as it is traced inw^ards, it may 

 be seen to pass gradually into the next layer. Those nuclei, 

 except in the deeper part of the layer, are not situated within 

 nerve-corpuscles, however small ; and the corpuscles which 

 can be detected in the deeper parts of the layer are so minute 

 as merely to invest the nuclei, except where the slender poles 

 are placed. This layer appears to constitute the superficial 

 parts of Arndt's third layer; and I am not prepared to 

 decide how far his second or sparsely nucleated layer may 

 not be included in it. I am tempted to say so because the 

 somewhat similar dense nucleation of a deeper stratum, 

 which I shall term the nucleated protoplasm of the primary 

 pale band, has escaped Arndt's observation, notwithstanding 

 his attention having been called to the subject by Meinert's 

 account of " Kornerschichten.'" This external layer of 

 ' Arndt, in Schultze's 'Archiv/ vol. v., p. 416. 



