Addendum 2t>5 



?'.'//"' nj'Ci'll I. mill nut nm. 



The cell arrangement is distinguishable from that of the motor area in three ways. First, 

 there is a layer of elements corresponding to the external layer of large pyramidal cells in man, 

 a layer which, as I have mentioned, is absent in the motor area. The cells do not approach the 

 Betz cells in magnitude, but they stand out plainly because they are much larger than the 

 surrounding elements. 



In the second place, the layer of giant or Betz cells becomes altered. It is true that cells 

 pertaining to the giant category are still present, and it is remarkable that they can be followed 

 along the floor of the suprasylvian sulcus almost to its posterior extremity, but such cells cease 

 In be arranged in nests; they are of the solitary type. Setting aside these "giant" elements, 

 the fundamental cell in the layer is one similar in size, shape, and general appearance to those 

 noted in the above-mentioned external layer. 



Thirdly, between these two layers of pyramidal cells a definite collection of small and indistinctly 

 stained elements, which one is forced to regard as representative of the stellate layer of man, is 

 intercalated. 



/V/>/-' .1 f fn ni/i' ment. 



In my examination of the primate cortex I noticed that the postcentral or sensory area was 

 remarkable in containing numbers of fibres in the interradiary plexus, of larger calibre than any 

 to be found in the precentral or motor area, but at the same time the latter cortex had a great 

 advantage in point of general fibre richness. In the cat conditions are quantitatively though not 

 qualitatively changed. If it were possible to enumerate the fibres, the crucial cortex might rise 

 superior to the postcrucial, but in the latter the wealth of gross fibres is so great that, in sections 

 stained for the display of nerve fibres, it stands out more prominently than does any in the rest 

 of the brain ; it was for this reason that one first imagined that this strip of territory belonged 

 to the motor area. However, since the fibre of gross size, as in the primate brain, is the dominant 

 constituent in sensory cortex ; also, since the fibre arrangement is associated with a special type 

 of cell lamination, I feel justified both in granting independence to the area, and in regarding it 

 as the homologue of the primate postcentral area, 



Distribution. 



The area is somewhat extensive, and, having no definite relations to named fissures, reference 

 to the figures on Plates 1 a and 2 a will be necessary to a comprehension of its distribution. 



On the mesial surface, it does not appear. 



On the dorsal aspect, it forms a posterior buffer to the motor area, it is thin towards the 

 middle line, but externally it expands and oversteps the outer fork of the lateral (ansate) fissure to 

 cover a considerable portion of the suprasylvian gyrus. And, as I have already stated, this type 

 of arrangement runs along the whole length of the floor of the suprasylvian fissure. 



Laterally, it covers most of that field of cortex inserted between the coronal and diagonal sulci. 



PARIETAL AREA. 



The designation " parietal " is being attached to a field centred on the marginal gyrus, and 

 interposed between that just described and the visual area. It is readily defined and has the 

 following distinctive characters : 



Fibre Arrangement. 



Examining a transverse section passing through the centre of the area, stained for nerve fibres, 

 it is at once noticed that the cortex is pallid compared with that of the postcrucial field this 



C. 34 



