56 
MR. W. BE VAN LEWIS ON THE COMPARATIVE 
cells, was most highly characteristic of motor areas.'" We have acquired from the 
foregoing examination sufficient data for mapping out approximately the relative areas 
of the five- and six-laminated cortex in the Pig, Sheep, and Cat; and the subjoined 
table gives the information necessary for the comparison of such results :— 
Area of Jive-laminated cortex. 
The Pig. (Figs. 1, 2, 3.) 
1. Anterior portion of superior lim bic arc in front of the crucial sulcus. 
Fig. 1 (7-19). 
2. Frontal lobe. 
3. Ascending parietal convolution. 
4. First and second parietal convolutions united in front of Sylvian fissure. 
The Sheep. (Fig. 4.) 
1. Anterior portion of superior limbic arc in front of the crucial sulcus. 
2. Frontal lobe. 
3. Ascending parietal convolution. 
4. First parietal convolution (Sylvian). 
The Cat. (Figs. 5, 6, 7.) 
1. Anterior portion of superior limbic arc in front of the crucial sulcus. 
2. Frontal lobe. 
3. First parietal or Sylvian convolution. 
4. Anterior extremity of second parietal convolution. 
5. Anterior extremity of fourth parietal or sagittal convolution. 
From this summary it is evident that, whilst in all these animals corresponding 
portions of the limbic and the whole of the frontal lobe are framed upon the same 
plan, the ascending parietal convolution partakes of this formation in the Pig and 
Sheep alone ; the first and partly the second parietal convolution is (in front of the 
Sylvian fissure) so constructed in all these animals, whilst a well-developed area of the 
same formation occupies the anterior extremity of the fourth or sagittal convolution in 
the Cat. It is interesting- to note here the fact that the crucial sulcus forms in all 
these animals alike a boundary fine betwixt the two typical laminar arrangements of 
the vertex, and marks at its commencement the transition of the one formation into 
that of the other in the limbic lobe. In summarising, as above, the areas of the five- 
lam mated cortex, with its coextensive nested series of ganglionic cells, due regard 
must be paid to the varying richness in development of the latter formation. In the 
diagram accompanying this memoir attention has been paid to this point, the dark 
shading indicating the rich developments of this formation ; the paler shading covers 
regions where the same formation is poorly developed. Guided by these diagrams, let 
us summarise for comparison the limits of the richly-developed motor cortex in each 
animal under consideration. 
* Log. cit. 
