274 The Cerebral Cortex in Sus Communis 



VISUAL AEEA. 



The visual area of the pig is distributed in the usual waj' over the upper segment of the 

 occipital lobe. On the mesial surface, the conjoint calcarine and intercalary sulci form a long 

 boundary, and looking in the frontal direction, it is interesting to notice that the area is directed 

 on to the convexity by the intercalary offshoot proceeding to join the "suprasylvian" fissure; inferiorly, 

 visual cortex shuns the rhinic and postrhinic fissures. Sweeping out on to the convex surface, the 

 area disregards the isolated, so-called "lateral" sulcus, and assumes the same relation to the so-called 

 "suprasylvian" sulcus, that it has to the lateral in the case of Canis and Felis an important 

 variation in distribution calling for comment later. 



Concerning the histological characters by which this cortex is recognised, one feature of particular 

 interest, and one by which the area can be mapped out alone, is the extraordinary linear formation 

 to be seen in nerve fibre sections, to which I referred in my opening remarks. This is represented 

 in the accompanying microphotographs, and although I personally have seen nothing like it in the 

 human brain, it may be indicated by calling it a very much modified line of Kaes (vide figure 3, 

 in a recent paper by that author, Neural. CentrcdbL, 1904). Studied in a fair transverse section of 

 a gyrus the formation lies about a third of the way down between the surface and the line of 

 Gennari ; it thus differs from the line of Bechterew which is placed near the surface close below the 

 zonal layer, it appears as a compact fasciculus made up of a dozen or more commingled fine 

 medullated and coarse varicose fibres, and is alike at all parts of the gyrus, crown, lips, and 

 sulcal walls. It is remarkable that the line appears interrupted, and this calls for explanation. 

 Clearly we cannot regard the formation as a stratum or layer in the strict sense of the term, for if 

 it were such the line would not be broken on transverse section : to an understanding of the 



o 



structure it is necessary to imagine what a section made parallel to the surface might display. Now 

 although I have not prepared such sections, yet, judging from what I have seen in portions of 

 cortex cut obliquely, I think we should find a series of separate fasciculi running parallel to one 

 another, not in straight lines, but sinuously, hence the apparent interruption, investing the gyri 

 somewhat like hoops round a barrel. The connections of these fasciculi for the present remain 

 obscure, nor would I hazard an opinion on the function they subserve; I will only repeat that they 

 traverse the visual cortex in its whole extent and that they are most readily studied in the sulcus 

 lateralis 1 (suprasplenialis). 



In other respects the fibre arrangement resembles that found in the other animals examined. 

 There is a distinct line of Gennari, but it is rather a thin one, and not nearly so marked as in 

 man or the ape ; it also lies closer to the white substance, separated by a zone containing the usual 

 large, obliquely-placed optic fibres. 



The cell lamination does not show any departure from the common formation. Pyramidal or 

 pyriform, pale-stained, but large solitary cells of Meynert are present in the depths. There is an 

 equivalent of the stellate layer, and above this a layer of medium-sized, erect, and well-defined 

 pyramidal cells. 



Search for something special in the cell lamination to fit in with the curious line I have 

 described proves fruitless. 



SENSORY AREA. 



If the so-called " suprasylviau " sulcus be followed from behind forwards, it will be seen to fork 

 anteriorly; the area partially enclosed by these two frontal limbs, crosshatched in the diagrams, is 

 covered by cortex which I look upon as representing the "sensory" cortex of other animals. The 

 peculiar fibre arrangement constitutes my chief ground for this assumption; it is quite different from 

 that of surrounding parts, and, in particular, it is distinguishable from that obtaining in the motor 

 cortex, in presenting a far greater wealth of gross fibres running in all directions, an arrangement 



