194 EDWARD HORNE CRAIGIE 
pyramidalis (III) consisting of typical, deeply-staining, pyramidal cells 
lying closely together, which corresponds to the third layer of Brodmann 
(09). In the rodent brain, the lamina granularis externa (II), or 
second layer of Brodmann, is always indistinct, and it is almost im- 
possible to distinguish it from the lamina pyramidalis (III). Beneath 
the lamina pyramidalis, the lamina granularis interna (IV) is situated, 
composed of crowded, deeply-staining, small granules, somewhat re- 
sembling glia-cells. Below this layer, there is the lamina ganglionaris 
(V), which has dispersed, large-sized, deeply-staining pyramids. Next 
to the lamina ganglionaris, there is the lamina multiformis (VI) with 
polymorphous cells. 
MATERIAL AND METHODS 
The material consisted of eight of the ten brains used in the 
previous study (’20), to which reference is made above. These 
were numbered 16, 23, 24, 26, 31, 55, 56, 58, for the last four 
of which the writer is indebted to The Wistar Institute. The 
forebrains of the remaining two specimens used in the earlier 
work were, unfortunately, not in good enough condition for 
study. A full account of the animals from which these brains 
were obtained, as well as of the technic employed in preparing 
them and of the method of measuring the capillaries, is given 
in the former paper. It will be sufficient to repeat here that 
nos. 23, 24, 31, and 58 were male albino rats, nos. 16, 26, 55, 
and 56 females. Numbers 16, 23, 24, and 26 were obtained in 
Toronto, while the remaining four, as mentioned above, were 
secured at The Wistar Institute. The microscope, lenses 
(Leitz no. 7 objective and no. 3 ocular), and square-ruled mi- 
crometer employed in making the measurements were the same 
ones as were used before, but owing to the thinnesss of the 
cortical laminae, it was found much more convenient to measure 
the capillaries enclosed in only one half of the large square on 
the micrometer. Hence the measurements made were the total 
length of the capillaries enclosed in an area of 3 x 189? sq. u 
in each section, the length of one edge of the micrometer square 
being 189u. As before, such measurements were made in the 
same region of each of ten successive sections, and as these 
sections were 20, in thickness, the sum of the (10) readings 
gave the total length of the capillaries in a block of tissue of 
the volume } x 189? x 200 ¢. u. These results are shown’in the 
accompanying table (table 1). 
