PLATE VII.

FIG. 1. Brain of the hog, upper surface. 2. Under surface of ditto. 3. Brain of the sheep. 4. Upper surface of the brain of the horse. 5. Under surface of ditto.

These five figures are reduced to about one-half the natural diameter.

PLATE VIII.

FIG. 1. Upper surface of the brain of a middle-aged man; a. is continuous with the fissure of Sylvius; b. with a sulcus situated before the island of Reil; c. with one in the middle lobe. To the left the convolutions are sliced off.

FIG. 2. The island of Reil, as seen in the Sylvian fissure. 3. The human medulla oblongata and fourth ventricle, the cerebellum being removed. a. Posterior pyramids. b. Valve of Vieussens, forming the middle lobe of the cerebellum. c. Posterior crura of the cerebellum, formed by the posterior columns of the cord. d. Anterior crura of the cerebellum going to the pons Varolii. e. Third ventricle. f. Pineal gland.

FIG. 3. The inferior surface of the human brain, to the right, seen as when removed from the skull, to the left dissected to show.-a. The anterior commissure and its anterior and posterior fibres. b. The olfactory nerve and its roots. c. The island of Reil and the course of the fibres through it from the crus of the brain. d. Medullary fibres passing between the anterior and middle lobes. e. The crus of the brain consisting of the crust before and without, and the tegmentum behind. f. The corpus striatum extending into the roof of the descending horn of the lateral ventricle. g. The hippocampus; and h. corpus fimbriatum, seen descending towards the inferior point of the middle lobe, the latter continued from the fornix i.; j. the little lobule of the cerebellum or flock appearing to originate the inferior membrane of the fourth ventricle. k. The pillar of the fornix descending to the corpus albicans.

PLATE IX.

FIG. 1. A vertical section in the middle line of the human brain, the corpus callosum and its convolutions above being removed, except a small portion, a, of the former behind, formed by the posterior lobes. Some of the grey matter of the corpus striatum is removed to show the radiating fibres of the crura. The tænia semicircularis, c, is seen dipping before towards the anterior commissure, d, as do the pillars of the fornix, e,

U

towards the mamillary bodies. ƒ. The fornix covering the velum and running behind into the lateral and posterior horns of the great ventricle. g. The soft commissure. h. The pineal gland. i. The hippocampus. j. The pons Varolii. k. The spinal cord and its component columns.

The human brain is represented in the above figures at about half its diameter

FIG. 2. Brain of the green monkey (simia sabæus). 3. A portion of the spinal cord in the neck of the ox, seen from behind. a. Posterior origins of a nerve. b. Spinal accessory. c. Theca and its dentate pro

cess. d. Anterior roots cut short.

FIG. 5. A simple galvanometer, formed by a stand and glass shade, some covered wire, two magnetized needles, reversed in their poles (astatic), and stuck in a scrap of paper, rotating over a graduated card, and suspended by means of a thread of silkworm, a bent pin, and a bit of a cork from a brass rod, the silk passing through a small quill in the coil.

FIG. 6. Representation of a piece of muscle, its natural electricity being negative at its transverse, and positive at its longitudinal surface. FIG. 7. Figure of the prepared leg of a frog, which may be made to contract when excited, by contact of its nerve with the pieces of zinc and copper.

LONDON:

PRINTED BY G. J. PALMER, SAVOY STREET, STRAND.

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