264 Tin' Crrthra/ Cortex in Fells Domesticus 



Cell Lamination. 



A plexiforin layer, and layers of small and medium-sized pyramidal cells, can be identified, 

 but they are devoid of special interest. 



On a level with the line of Geiinari is a good layer of sharply-stained pyramidal cells, not 

 so large as those at the same level in other cortical areas. They seem to correspond with the 

 human external large stellate cells. 



Below this comes a fairly broad layer of ill-stained, small cells, and there seems to be no 

 doubt it is a weakly developed homologue of the human stellate layer. 



But the cells which most of all characterise the visual cortex are large elements, indubitably 

 corresponding with the large, human, solitary cells of Meynert. They are numerous and form a 

 distinct layer ; on the whole their shape is pyramidal, but they may be stellate or polymorphous 

 and they contain numerous chromophilic elements. Along with these one occasionally observes 

 rounded processless elements, of large size, full of pale-stained Nissl particles. They are of doubtful 

 significance. 



The last layer, the fusiform, presents no special characters. 



Distribution. 



The cortex endowed with these qualities bears a close and evidently a very important relation 

 to two deep and constant fissures, situated on the inner and dorsal surfaces of the hemisphere, 

 respectively; they are the calcarine-intercalary complex of Elliot Smith (the splenial of other authors) 

 and the lateral. On referring to the figures reproduced these relations will be clearly understood. It 

 may be noticed that, on the mesial surface, the conjoined calcarine and intercalary fissures form 

 a limit, and an important point, unseen in a surface diagram, is that the visual cortex is con- 

 fined to the peripheral wall only of the tissural complex, the opposite wall being covered by another 

 type altogether, to be described later under the heading "limbic." 



Viewed from the caudal aspect, the lower limit lies level with the lower extremity of the 

 calcarine fissure, and a distinct interval separates it from the hinder extremity of the fissura rhinica 

 and from the occasional posterior offshoot of the same fissure. 



From these inner boundaries the area sweeps outwards over the marginal gyrus and round 

 the occipital pole ; then, gaining the convexity of the hemisphere, it is not arrested until the hinder 

 part of the sulcus lateralis is reached. 



POSTCRUCIAL OE SENSORY AREA. 



Professor and Madame Vogt, from an examination of the cortical nerve fibres of the kitten 

 and fully grown cat, have mapped out an extensive area in the frontal region, embracing the 

 motor area just defined and spreading from here backwards in the direction of the suprasylvian 

 and lateral sulci ; this they designate the "area precox anterior," because it is one of those parts 

 in which the contained fibres acquire their myelinic investment at a comparatively early date, but, 

 and this is a point I wish to emphasise, they seem to have made no serious attempt to effect 

 a further subdivision of the area. 



Now I must confess that my preliminary examination of sections stained for nerve fibres did 

 not suggest the existence of two separate areas, but on closer observation, and especially after a 

 collateral inspection of the cell lamination, I have arrived at the conclusion that the field is divisible 

 in much the same way as is the pre- and post-Rolanclic cortex of man and the man-like ape. 



