PLATE 19.

The Cerebral Cortex.

The left side of the figure shows the arrangement of the cells (the outer portions are stained with silver, the center with methylene-blue); the right side shows the arrangement of the fibers; the two portions are, of course, anatomically related.

The cells of the cortex may be divided into six layers: (1) Stratum zonale, containing small polymorphous cells of the Golgi type; (2) the first layer of small pyramidal cells; (3) the layer of medium-sized and large pyramidal cells; (4) the second layer of closely packed small pyr amidal cells; (5) the second layer of medium-sized and large pyramidal cells with a few giant pyramidal cells; (6) the lowest layer of polymorphous cells lying partly within the white substance.

The nerve-fibers of the cortex for the most part pass from the cerebral medulla into the cortex; collected into bundles they enter the second layer of cells, where their terminal fibrils end; these radial bundles (radii) therefore have a vertical arrangement. They are crossed at right angles by other fibers running parallel with the surface of the cortex and forming the so-called plexus of tangential fibers the superradial reticulum above the radii, and the interradial reticulum within the radii. The six layers are arranged as follows: (1) The stratum zonale, containing the most superficial layer of tangential fibers immediately under the pia mater; (2) the superradial reticulum, in the free upper border of which there is a robust layer of fine tangential fibers known as Bechterew-Kaes' stripe; this layer is composed entirely of very delicate transverse fibers, and contains the terminal fibrils of the radial bundles; (3) a dense collection of coarser tangential fibers (Baillarger's, Gennari's, Vieq d'Azyr's stripes, the latter being best developed in the cortex of the cuneus); (4) the interradial reticulum of tangential fibers; (5) the layer of closely packed radial bundles containing a few transverse fibers; (6) the medullary layer, containing the radiating white fibers (projection, commissural, and long association tracts) and the transverse short association bundles (Meynert's arcuate fibers).

PLATE 20.

A Cerebral and a Cerebellar Convolution.

Pass

FIG. 1.-Cerebral Convolution from the Center of the Anterior Central Convolution (carmin medullary sheath stain). The white matter is stained blue-black; the radial bundles (r) radiate in all directions and end in the cortex. ing from without inward, we distinguish the following layers: The outermost subpial layer (a); the zonal layer (2); the layer of pyramidal cells, which also present a radiating arrangement and contain Baillarger's stripe; the radiation of projection fibers (r), containing the outer and inner association layer (Meynert's arcuate fibers, M); and finally the dense network of white matter (F).

FIG. 2.-Cerebellar Convolution (Silver Stain). From the narrow medullary substance, which is stained black, a few isolated fibers are seen passing through the granule layer (yellowish-brown) to the cortical layer proper, which is stained yellow and is also very narrow. At the base of the cortical layer we see a row of cells of Purkinje, with their elaborate arborizations. (See Plate 18.) A few moss-like fibers (r) are shown in the cortex, and some individual granule cells at g.