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.