Iii the first place, the layer of small pyramidal cells exhibits a curious departure from the 

 condition we are familiar with in the brains of man and many other animals; it appears as a 

 prominent layer, visible under a very low power of the microscope, composed of deeply-stained and 

 rather large polymorphous (fusiform, triangular, quadrilateral, stellate) elements, with short processes 

 pointing in no particular direction. Cells to which they can be compared are those occupying the 

 prominent second layer in the lobus pyriformis of most mammals ; it must be understood, however, 

 that, in Sus, this formation is not confined to any special part, but has a universal distribution. 



Secondly, in describing the motor area, 1 shall have to mention that no real "giant" cells of 

 Betz exist. 



Another peculiarity is the prevalence of cells in all parts of the cortex, which are rounded or 

 oval in form, processless, and faintly stained. Whether these are to be regarded as undeveloped 

 elements, or as cells of a low type, it is difficult to say, but I may mention that as the pig 

 from which this brain came was twelve months old and almost fully grown it is not likely that 

 they are undeveloped cells. 



In the next place, I have noted outlying cells in the white substance beneath the cortex in 

 practically every convolution. 



Lastly, in the visual area, extraordinary superficially-placed bands of fibres, unlike anything I 

 have seen in the brain of Homo or any other animal, will call for special remark. 



MOTOR AREA. 



A\ ith no sulcus cruciatus to serve as an anatomical finger-post, and no typical "giant" cells for 

 a microscopic guide, I naturally have some misgivings about the correctness of my designation of 

 this field. But the area marked "motor" in the figures, bounded internally by the so-called "coronal" 

 sulcus, and externally by a cross-shaped presylvian sulcus, is coated by the nearest approach to the 

 motor cortex of other animals, and, in order that judgment may be passed 011 this conclusion, I will 

 give the structural characters at length. 



Cell Lamination. 



The plexiform layer may be slightly shallower than it is elsewhere and the succeeding stripe of 

 polymorphous cells less prominent. 



The third layer is deep and made up of clearly-outlined and sharply-stained medium-sized 

 pyramidal cells. 



A stratum containing numerous ill-stained, small, round or oval elements follows. 



Then comes the layer showing cells which I believe to be the equivalents of the giant cells of 

 Betz. Although these are relatively much smaller than the Betz cells of Felis and Canis, they are 

 still the largest present in the cerebral cortex of Sus ; the}* are pyramidal or pyriform, they show 

 three or four basal dendrites and a stout apical extension, they contain tine Nissl bodies, they 

 tend to occur in groups of two or three, and the layer they form collectively is not a promi- 

 nent one. 



Below this is another lamina of indefinitely-stained, small, rounded elements, and lastly, a layer 

 of fusiform cells the processes of which do not stain sharply. 



Fibre A rrangement. 



Although the cell lamination is not entirely what we expect in motor cortex the fibre arrange- 

 ment favours what we know of the localisation of this function. It is exactly like what has been 

 described in Felis and Canis. 



C. 35 



