In the posterior view we see that below the great mass of brain which is called the cerebrum there lies a smaller body, shaped much like a small turnip, called the cerebellum. or little brain, separated from the cerebrum by a firm, horizontal membrane called the tentorium (covering the cerebellum), on which the cerebrum rests.

The position of the tentorium can easily be ascertained in your own head by the fact that where it crosses the median line there is a little pro

jection of bone called the occipital knob, very prominent on some persons, barely perceptible on others. After locating the occipital knob, a horizontal line forward will give us the portion of the tentorium. When we carry this line forward just over the cavity of the ear, thus locating the tentorium, we easily recognize below it the rounded prominence on each side in which the two hemispheres or halves of the cerebellum lie, with a depression between them on the median line. To make these and other observations on the head (which no one should neglect), the hand should be placed firmly on the scalp, so that as it slides on the bone we feel the form of the skull beneath. In most persons a distinct depression will be felt along the line of the tentorium, separating the cerebrum and cerebellum - the cerebellum being located at the summit of the neck, and extending down about as low as the end of the mastoid process, which is the large, long prominence just behind the cavity of the

ear.

The cerebellum may be regarded as the physiological and the cerebrum as the psychic brain, for the cerebellum is void of intelligence and volition, but has important influences on the body. It may be considered, like the spinal cord, an intermediate structure between the controlling and conscious brain and the corporeal organs.

The tentorium does not entirely separate it from the cerebrum, for anteriorly it is open to permit the passage of the fibres which connect the cerebrum with the spinal cord and the cerebellum, fibres which pass up midway between the right and left ear, so that a bullet fired horizontally through from ear to ear would sever the connection of the cerebrum with the bodily organs, producing instant death. This will be understood by looking at the profile of the interior of the right hemisphere, on which we see the position of the pons and the medulla and their relation to the cerebrum by their ascending fibres. As these ascending fibres correspond to a position just above the cavity of the ear, and as they are the channels of all muscular impulses, the reader will perceive that breadth of head immediately above the cavity of the ear must be associated with muscular impulsiveness.

The position of the cerebrum in the cranium may be best understood by sawing the head in two horizontally, taking out the brain, and looking down into the base of

the skull, in which we see anteriorly a shelf for the front lobes, behind which are the cavities for the middle lobes, and behind that the rounded cavities for the cerebellum.

Thus the front lobe occupies the highest plane, resting on the vault of the sockets of the eyes, and extending back as far as the sockets. The middle lobe lies behind the sockets of the eyes and above the cavities of the ears, its base being as low as the bottom of the sockets. of

the eyes and corresponding nearly with the upper edge of the cheekbone, as it extends from the sockets to the side of the head just in front of the ears. In the posterior base of the skull, the reader will observe an opening (foramen magnum or large foramen) through which the spinal cord ascends. The spinal cord is exposed in the neck below the foramen.

Going back, we find the middle lobe rises higher, ascending over the cavity of the ear and resting upon the ridge of bone in which the apparatus of hearing is situated, thus reaching the level of the tentorium, on which the occipital lobe rests.

The bones of the cranium seen by looking down into the basis of the skull, as above, are the frontal bone over the eyes, the sphenoid bone, behind the sockets of the eyes, extending from the right to the left temple, the temporal bones, forming the ridge that holds the apparatus of hearing, and extending up about two inches on the side head, and the occipital bone at the back, between the two temporals, meeting the sphenoid bone in the centre of the base. The cerebellum rests in the deep double concavities of the occipital bone, and the spinal cord ascends through the large opening (foramen magnum in the middle of its base, assuming the form called the medulla oblongata.

When we fully understand this view of the base of the skull, let us look at it in profile, and observe the frontal bone connected by the coronal suture to the parietal and the parietal by the squamous or scaly suture to the temporal, and by the lambdoid suture to the occipital. The sphenoid or bat-wing bone appears in the temples by its wing, between the frontal and temporal, while in the centre of the base its solid body is between the frontal and occipital.

The sphenoid bone is in contact with organs of sensitive delicacy, refinement, and inspiration, the occipital with organs of vital force, the temporal with organs of appetite, excitement, and force, the frontal with organs of intellect and refined benevolence, the parietal with the organs of virtue, amiability, self control, and general strength of character, which make a superior person.

Modern anatomists do not divide the brain into front, middle, and occipital lobes as would seem most natural, by erecting vertical lines from their bases, but follow up the oblique courses of the convolutions so as to extend the front lobe into the upper surface of the brain, and extend the middle lobe from the middle of the upper surface backward into the region of Self Confidence, giving the name of temporo-sphenoidal to its lower portion behind the sockets of the eyes and over the ears, which name is taken from the temporal bone, that contains the apparatus of hearing, forming the middle of the basis of the skull, and the sphenoid bone, which lies just back of the sockets of the eyes, supporting the front end of the lower portion of the middle lobe, called temporo-sphenoidal.

The sphenoid bone thus sustains the region of Sensibility, while the temporal bone lodges the organs of the most sensual, selfish, and violent impulses, the action of which is downward into the muscular

and visceral organs of the body. The sphenoid bone as it extends up touches the base of the front lobe and of the Ideal region, where it assumes the name of Somnolence. (See the profile view of the cranium.)

The upper portion of the middle lobe has been given the name of parietal, as it has a general correspondence with the parietal bones, while the occipital lobe has a general correspondence in position with the occipital bone, as will be seen by comparing the plan of the brain seen in profile with the engraving of the cranium.

The plan of the brain is given, instead of an engraving of the actual convoluted surface, to simplify the study to the learner. An examination of the brain itself or of a good model offers at first sight such a vague and irregular mass of convolutions, differing so much in different brains, that any systematic arrangement would seem impossible. But by studying the subject more extensively and considering the structure of the simpler brains of animals, in which the complexity of the human brain is reduced to simpler forms, a mode of grouping and classifying the convolutions has been adopted by anatomists which is illustrated by the engraving, in which we see, not the numerous convolutions of a well developed human brain, but the groups in which they have been arranged by the aid of comparative anatomy.

The front lobe is grouped into the superior, middle, and inferior convolutions, or groups of convolutions, and the ascending frontal; but the inspection of a brain would show an irregularity of forms in which a casual observer would be puzzled to trace this arrangement.

The appearance of the brain, divested of its membranes, when we look upon its superior surface, is shown in the annexed engraving,

in which it is presented as it lies in the head when the cranium and membranes are removed which form the rim of the figure. The front lobe is the upper portion, and the outline of the nose is just visible. In the full exposition of this subject hereafter in a larger work, I propose to show the exact seats of the various functions in the convolutions, which are much more irregular than the angular figures we make on the surface of the head to show the average positions of organs. Of course no intelligent person supposes the psychological maps and busts of the organs to be representations of the brain, or anything more than approximations to the true interior organology, which, however, do not lead to any great error, as adjacent portions of convolutions have very analogous functions.

When we place the brain on its upper surface and inspect the bottom, we observe at the back the cerebellum, which dips into the

neck, the middle lobe, which is over the ears and the side face, and the front lobe, which rests over the eyes.

We observe posteriorly the medulla oblongata, on the face of which we may observe the crossing of the fibres, and on the side of which we observe the origins of many nerves. Above the medulla we observe the pons Varolii, just above which we observe the fibres ascending to each hemisphere under the name of crus cerebri, or thigh of the cerebrum. Next we see the optic nerves crossing on the median line, the olfactory nerve, running under the front lobe, which is separated by the fissure of Sylvius from the middle lobe. There is also a glimpse of the corpus callosum at its anterior end, obtained by pulling the front lobes apart at the median line.

Let us next cut through the head exactly on the median line, dividing the right and left hemispheres, and look at the inner face of the right hemisphere. We observe that it has convolutions, just like the exterior surface, which do not join across the median line, but are separated from those of the left hemisphere by a firm membrane