AND

EXPLANATION OF THE ILLUSTRATIONS.

PLATE I.

FIG. 1. The brain, its coverings having been removed-viewed from above.

AA. The two hemispheres, with their convolutions; a, the frontal lobe, a', the middle lobe, a”, the posterior lobe.

1. The occipital bone; 1', suture between the occipital and parietal bones.

2. The parietal bone; 2', suture between the parietal and frontal bones.

3. The frontal bone; 3', the frontal sinuses.

FIG. 2. The basis of the brain viewed from below.

AA, a, a', a", same as in fig. 1. a'", the sylvian fissure, separating the frontal from the temporal lobe.

BB. The cerebellum, with its two hemispheres and convolutions. C. The medulla oblongata, showing the median division into two lateral halves nearest to the fissure are the corpora pyramidalia, containing anterior fibres of the spinal cord; then come the corpora olivaria, containing lateral fibres; and behind these lie the corpora restiformia, containing posterior fibres of the spinal cord.

D. The Pons Varolii, the system of fibres connecting the cerebrum and the cerebellum.

b. The olfactory nerve and its bulb.

c The optic nerve.

d. The auditory nerve.

c. The nerve belonging to the sense of taste. (Glosso-pharyn

geus).

PLATE II.

FIGS. 1 and 2. Two skulls cut open horizontally, their basilar parts viewed from above.

A. The anterior fossa, seat of the frontal lobe.

B. The middle fossa, seat of the temporal lobe.

C. The posterior fossa, seat of the cerebellum.

D. The large occipital hole (foramen magnum), through which the spinal cord enters into the brain.

a. The frontal bone.

a'. The zygomatic arch.

b. The sphenoid bone.

c. The temporal bone.

d. The petrous portion of the temporal bone, separating the middle and posterior fossæ of the skull. Within the os petrosum lie the auditory nerves and apparatuses for the conveyance of sound.

e. The occipital bone.

f. The clivus, the part of the basilar bone on which the medulla oblongata and pons varolii repose.

N.B. FIG. 1. The basilar portion of the skull of a man of narrow intellect, though entirely removed from cretinism or idiocy. He was convicted in Saxony of arson, but on account of defective understanding, condemned to loss of liberty only. He was seen by me before his trial, and, after his death in the house of detention, I procured this drawing of his skull. The cast of his head is in my possession. FIG. 2. The basilar portion of the skull of a man of average intellectual capacity. The supra-orbital plates of these skulls show a remarkable difference as to their size; whereas the other fossæ of the skulls are nearly similar.

PLATE III. ·

FIG. 1. Brain of the celebrated German mathematician, Gauss. FIG. 2. Brain of a German handworker. The drawings are from a German work, 'Das Leib des Menschen,' by Professor Reclam. They show a great difference in respect to the number and arrangements of the convolutions.

been formed. These circumstances are mentioned in explanation of the references in the following pages to German authorities in anatomy and physiology, and to German heads in illustration of the text.

R. R. N.

April, 1873.