FIG. 276.-SECTION OF CEREBRAL CORTEX OF YOUNG RABBIT, PREPARED BY GOLGI'S METHOD. (G. Retzius.)

9, pyramidal cells of second and third layer sending their axis-cylinder processes, a, a, towards the white centre; d, d, dendrons of pyramids; p, polymorphous cell of fourth layer, with its axis-cylinder extending towards the surface; n, n, neuroglia-cells.

Figs. 277 to 282 are taken by the author's permission from Ferrier's Functions of the Brain, 2nd edition. They are from preparations and drawings (from the monkey's brain) made by Mr. Bevan-Lewis, and are magnified about 145 diameters.

marked (5, 6), the neuroglia-layer having a very distinctly reticular aspect, and being in part beset with small cells. All the rest of the thickness of the grey matter appears mainly to contain long conical cells (fig. 282, 5; fig. 283, 3, 4), the distal processes or apices of which

FIG. 283.-SECTION ACROSS THE HIPPOCAMPUS MAJOR, DENTATE FISSURE, DENTATE FASCIA AND FIMBRIA. (Henle.)

Gh, part of the gyrus hippocampi or uncinate convolution; Fd, fascia dentata, or dentate convolution; between them is the dentate fissure; Fi, fimbria, composed of longitudinal fibres here cut across; 1, 2, medullary centre of the hippocampal gyrus prolonged around the hippocampus, H, as the so-called alveus, into the fimbria; 3, layer of large pyramidal cells; 4, their processes (stratum radiatum); 5, reticular neuroglia (stratum laciniosum); 6, superficial medullary lamina, involuted around the dentate fissure; **, termination of this lamina, the fibres here running longitudinally; 7, superficial neuroglia of the fascia dentata; *, ring of small cells within this (stratum granulosum).

are prolonged into fibres which lose themselves in the superficial layer of neuroglia. The pyramidal cells rest upon the white centre, bere known as the alveus (1), which is the part of the hippocampus seen

within the ventricle, and which is prolonged externally into the fimbria (Fi), where its fibres become longitudinal in direction.

In the dentate gyrus (fascia dentata, fig. 283, Fd) the pyramidal cells are arranged in an irregularly radiating manner, occupying the centre of the convolution, and surrounded by a ring of closely packed small cells (*). External to these is a thick layer of superficial neuroglia (7).

The olfactory tract is an outgrowth of the brain which was originally hollow, and remains so in many animals; but in man the cavity has become obliterated, and the centre is occupied by neuroglia, containing no nerve-cells. Outside the central neuroglia lies the white

FIG. 284.-SECTION ACROSS A PART OF THE OLFACTORY BULB. (Henle.) 1, 3, bundles of very fine transversely cut nerve-fibres, forming the flattened medullary ring, inclosing the central neuroglia 2: this is the anterior continuation of the olfactory tract; 5, white layer with numerous small cells (granules); 6, mitral layer; 7, layer of olfactory glomeruli, t, tt; 8, layer of olfactory nerve-fibres, bundles of which are seen at passing through the cribriform plate of the ethmoid bone.

or medullary substance, consisting of bundles of longitudinal white fibres. Most externally is a thin superficial layer of neuroglia.

The olfactory bulb (fig. 284) has a more complicated structure. Dorsally there is a flattened ring of longitudinal white bundles inclos