199 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 
which belong to the same vertical bundles, and which bend 
round into the gray substance at the same level, may diverge 
in their passage through the white substance, so as to enter 
the gray at different points of the same horizontal plane. 
(2) Intermingling of fibres takes place by the diversity of 
their course through the gray substance, viz., either (a) by 
the formation of simple networks (without ganglion-cells) ; (0), 
or by strands which traverse considerable portions of the cord, 
either commissurally so as to connect the two halves of the 
cord, or vertically so as to connect portions of the cord 
situated at different levels. 
(3) Special arrangements which probably serve in part, at 
least, to connect nervous fibres of different function are seen 
in the ganglionic cells with their close networks between 
them. One of these groups of cells, if it could be taken out 
entire with its nervous attachments, would be like a rolled-up 
hedgehog with its spines. 
(4) Finally, must be enumerated the mode in which the 
fibres of the posterior roots enter the cord, with their decus- 
sations and their further horizontal and vertical course. 
3. Distinction of two Nerve-centres in the Brain.—Betz 
(* Centralblatt,’ 1874, p. 578) seeks to distinguish in the 
human brain two limited regions, which he regards as special 
nervous centres. One of them is thus indicated. The fissure 
of Rolando divides the cerebral surface into two parts, the 
anterior of which is distinguished by the abundance of large 
pyramidal ganglionic cells, the posterior by the predominance 
of the nuclear layers. Of this anterior half the posterior 
portion forms a region, having certain peculiarities. The 
region is limited by the whole of the anterior central convo- 
lution and the upper end of the posterior central convolution, 
and extends to the inner surface of the hemispheres, where it 
forms a constantly present clearly defined lobe. 
Again, the posterior portion of the half of the hemisphere, 
lying behind the fissure of Rolando, forms an equally distinct 
but larger region. This extends through the cuneus, the 
hinder parts of the lobus lingualis and lobus fusiformis along 
the whole outer extremity of the occipital lobe, and also into 
the transitional conyolutions which are found in the external 
occipital fissure. 
The former of the special regions thus indicated contains 
cell-forms of a very peculiar kind, till now undescribed. They 
are the largest pyramidal cells seen anywhere in the nerve- 
centres, and might be called “ giant pyramids,” being ‘05 to 
‘06 m.m. broad, and ‘04 to ‘012 m.m. long. Each possesses 
two principal processes, and 7 to 15 secondary protoplasmic 
