v ] Distribution of Vitmo-J'sye/ttc Cortex 120 



Unfortunately 1 am unable to give an account of the appearances presented by these 

 cells in Golgi specimens, because Ramon y Cajal does not figure or describe them in his 

 work and I have not been able to undertake the preparation of such specimens myself; 

 their great size, however, and their limited distribution suggest that they are of functional 

 importance. Their presence accounts in a large measure for the abundant plexus of large 

 nerve fibres which I have described as an important character of this area, and there can 

 be little doubt that they stand in relation to subjacent fibres pertaining to the optic 

 radiations. 



The layer of stellate cells is of like depth and contains elements similar in appearance 

 to those noted in the same layer in the calcarine area. 



It is difficult to divide the remainder of the cortex into layers ; medium-sized pyramidal 

 and ordinary fusiform cells are present in abundance, and the former preponderate in the 

 outer and the latter in the inner part. 



It is important to notice that with the exception of an occasional large cell, possibly 

 a dislocated solitary cell of Meynert, no cells of large dimensions are to be found in the 

 deeper layers of this cortex. 



In conclusion I have to mention that the aggregate depth of this cortex is greater 

 than that of the calcarine type. 



DISTRIBUTION OF THE VISUO-PSYCHIC TYPE OF CORTEX. (Text-figure 11.) 



Although this type of cortex has decided and distinctive characters in the central parts 

 of the field the exact demarcation of its distribution is not accomplished without difficulty ; first, 

 because the disappearance of large fibres and the general transitional changes which the area 

 undergoes at its borders are gradual instead of abrupt: especially is this the case where 

 the field joins the parietal and temporal areas ; and, secondly, because the occipital lobe is 

 of such an awkward shape, that it is almost impossible to divide it into a series of sections, 

 all of which will show the cortex cut at right angles to the plane surface and free from 

 the damaging effect of obliquity. However, having examined so great a number of brains, 

 and having followed different lines of section in different cases, I think I have arrived at 

 a definition of the area which is more than approximately correct. 



Starting with that part of the area situated on the mesial surface of the hemisphere, 

 above the calcarine fissure, it is to be observed that it does not extend on to any part of 

 the gyrus fornicatus, or of the precuneus, lying above the anterior division or stem of the 

 fissure indicated : indeed, it is not found even on the upper wall of this portion of the 

 fissure. Proceeding backwards, however, we find that it makes an appearance on the gyrus 

 cunei (i.e. the deep cuneo-limbic annectant gyrus found at the point of junction of the 

 parieto-occipital and calcarine fissures) ; and above this point the floor of the parieto-occipital 

 fossa, not in its entire extent, but almost as far up as the margin of the hemisphere, may 

 be described as a boundary. From which it follows, that all that portion of the cuneus 

 which remains uncovered by a visuo-sensory type of cortex is occupied by a visuo- 

 psychic type. 



This distribution, however, does not obtain invariably, because in one of the brains which 

 I examined a considerable extent of the surface of the cuneus, lying in the angle formed 

 c. 17 



