Frontal lobe

“ The average weight of the hemispheres separated from the rest of the brain is 1019 grammes in man (frontal lobe 428, the rest 591) , and 930 in woman (frontal lobe 384, rest 546) . Here, atrophied brains (except general paralytics) have been weighed with others, which lowers the average total weight without altering the proportion. Thus, the rest of the cerebral hemispheres exceeds the frontal lobe by 163 grammes in man and 162 grammes in woman, which means that in man the frontal lobe constitutes 42 per cent. of the cerebral hemispheres and in woman 41.3 per cent. ”

“ Hence the occipital action of the brain generates vital force and diffuses it in the body, while the frontal region, in its aggregate tendency, expends the vital force—the greatest tendency to expenditure being in the most extreme frontal region. Both the front lobe and the anterior extremity of the middle lobe tend to the expenditure of vital force and destruction of health, and it is absolutely necessary to life that the action of the front lobe should be suspended one-third of our time by sleep, without which it would exhaust vitality. ”

“ In this way an air-space, the frontal sinus, is formed, whose development is thus directly correlated to the two factors of brain development and size of the teeth. If the frontal lobes are narrow in a macrodont skull, then the foundations of the outer or malar piers of the orbital arch must be extended outward as well as forward, the external angular process becoming a prominent abutment at the end of a strong, low-browed supraorbital arch, whose overhanging edge gives to the orbital aperture a diminished vertical height. ”

“ As to the external anatomy, whilst too little importance has perhaps been assigned to the points of difference which the very widely-differing heights of the hemispheres, the very widely-differing antero-posterior diameters of the corpora callosa, and of the frontal lobes, and the very widely-differing absolute weights of the two brains, constitute, too much seems to have been given to the "absence of an external perpendicular fissure," to the "presence of a lobule of the marginal convolution," and to the lesser relative size of the nerves in the human brain. ”

“ By observations and experiments similar to those employed in localizing the sensory and motor areas, the inhibitory centers have been localized in the frontal lobes of the brain. The development of these lobes, as compared with other parts of the brain, is conspicuous in man; as a rule, also, great intellectual power is associated with great frontal development. ”

“ The frontal brain or cerebrum contains the centers for the sensory organs, also the motor centers which supply the driving impulses for the muscular activities of the body, and in the occipital and frontal lobes, the centers for the higher and highest qualities of mind and soul, which constitute the governing and restraining faculties on which depend the powers of self-control. ”

“ The postfrontal forms the antero-lateral boundary of the supratemporal fossa.
Articulating posteriorly and laterally with the parietal and the postfrontals, and forming the highest point of the skull, is the single frontal bone (24) , which, like the parietal, is paired in the embryo. It is a heavy bone whose dorsal surface is flattened posteriorly, deeply concave in the middle region, and drawn out into a long projection anteriorly. It forms part of the roof of the cranial cavity and articulates ventro-laterally with the alisphenoid and anteriorly with the prefrontals and nasals. ”

“ Fig. 15.—Cranium at birth, showing sutures and fontanelles.
The frontal bone, as its name implies, forms the fore part of the head or forehead. It joins the parietal bones above and the temporal bones on either side. At the lower edge are the supra-orbital arches, each with a supra-orbital notch or foramen on its inner margin for the passage of the supra-orbital vessels and nerve, the nerve most affected in neuralgia. Just above the arches on either side are the superciliary ridges, behind which, between the two tables of the skull, lie the frontal sinuses. ”

“ The intelligence and all the special senses, except the sense of touch already spoken of, are gathered together compactly in the head, where they are carefully protected with bony tissue. Covering the brain is the skull or cranium, which is made up of eight bones, the frontal, the occipital, two parietal, two temporal, the sphenoid, and the ethmoid, while the bones of the face are fourteen in number, two nasal, two superior maxillary, two lachrymal, two malar, two palate, two inferior turbinated, the vomer, and the inferior maxillary. ”

“ The occipital and frontal muscles, united by a thin aponeurosis, cover the whole upper cranium and are known as the occipito-frontalis muscle. At the back this is attached to the occipital bone, while in front it interlaces with various face muscles. It is a powerful muscle and raises the brows, wrinkles the forehead, and draws the scalp forward. Long hair grows on the skin over it as a further protection against blows upon the skull and sudden variations in temperature. ”

“ The truth is, supposing the brain to unite, instead of separate, the frontal line of the face and the axial line of the body, the bending of the continuous right line formed by them in the lowest vertebrate fishes into the two parallel lines in man, the one facio-abdominal and the other occipito-dorsal, is not by angles at all, but by curvatures, and the union of the parallels is by an arch over the head. The arc in each case is a greater or less part of a circle, according to the grade of intellectual and moral development. ”

“ Not only do the cerebral hemispheres overlap and the olfactory lobes and cerebellum, but they extend in advance of the one and further back than the other. The posterior development is so marked, that anatomists have assigned to that part the character of a third lobe; it is peculiar to the genus Homo, and equally peculiar is the posterior horn of the lateral ventricle and the 'hippocampus minor,' which characterise the hind lobe of each hemisphere. ”

“ Physiologists tell us that the human brain is double, that the right and left lobes act in a degree independent of each other—the right lobe of the brain controlling the physiology of the left side of the individual from head to heel, while the left lobe exercises a like dominion on the opposite side. ”

“ The basis of the middle lobe, which is the most physiological portion of the cerebrum, being devoted to the sensibility, appetites, and muscular impulses, is that which first presents itself, being the first outgrowth from the great inferior ganglion or summit of the spinal system. As human brains degenerate to a lower type they approximate this form. ”

“ In the skull, besides the larger openings we have spoken of, you will find several small holes leading from the outside of the skull into the inside of the brain-case. Some of these holes are filled up during life by blood-vessels, but in others run those delicate white threads or cords which you have already learnt to call nerves. Nerves are in fact branches of nervous material running out from the brain or spinal cord. Those from the brain pass through holes in the skull, and at first sight seem to spread out very irregularly. Those which branch off from the spinal cord are far more regular. ”

“ It is generally admitted that no very strict line of demarcation is traceable between the middle and posterior lobes; anatomists being content to accept Cuvier's curt definition:—
"La partie du cerveau située au-dessus du cervelet est ce qu'on nomme le lobe postérieur du cerveau." ”

“ The head contains a large nerve centre, corresponding with the brain, which is produced backwards into a chord, corresponding to the spinal chord. In the head, sense organs are clearly distinguishable; there is a well-marked eye, an equally clear ear, and a less clearly marked olfactory organ. Besides this, the spinal-cord is supported below by a rod-like structure, called the notochord. In the vertebrate embryo this structure always precedes the development of the true vertebral column, and in the lowest forms is persistent through life. ”

“ First, the occipital foramen being situated entirely at the base of the cranium of man and not carried up behind, as in the other vertebrates, causes his head to be posed at the extremity of the vertebral column as on a pivot, not bowed down forward, his face not looking towards the ground. This position of the head of man, who can easily turn it to different sides, enables him to see better a larger number of objects at one time, than the much inclined position of the head of other mammals allows them to see. ”

“ Great changes have been effected in the head, resulting in a diminution of the cranial flexure. This diminution is nevertheless apparent rather than real, and is chiefly due to the rapid growth of the rudiment of the cerebral hemispheres. ”

“ As no function, then, either of brain or gland, can be carried on without a due supply of blood, it will follow that position may materially influence the integrity of these functions. The seat of the organs I have alluded to, if cranial development supports me, may be determined on the fore part of the head, behind the os frontis, portions of the cerebral mass which, in the supine position, are usually most elevated above the centre of circulation. “The more noble the faculties, the higher are the organs situated.” ”

“ Luys holds that the brain, as a whole, changes its position in the cranial cavity according to different attitudes of the body, the free spaces on the upper side being occupied by cerebro-spinal fluid, which, obeying the laws of gravity, is displaced by the heavier brain substance in different positions of the body. ”

“ One of these tracks was cut on each side, the surgeon explained, because it would give equal expansion to the two sides of the brain, and because it would cause death to cut through the middle of the top of the head, where lies "the superior longitudinal sinus." He left, therefore, the solid track of bone through the middle, and cut two grooves or tracks through the bone, one on either side, where nature (when she does not make a mistake) leaves soft or yielding edges, by means of which the normal skull expands to fit the needs of the brain within. ”

“ The medulla is part of the brain stem.
This was only one of the difficulties which had to be overcome. The eyes are set on the pre-fulcral lever of the head. For our safety we must be able to look in all directions—over this shoulder or that. We must also be able to turn our heads so that our ears may discover in which direction a sound is reaching us. In fashioning a fulcral joint for the head, then, two different objects had to be secured: free mobility for the head, and a safe transit for the medullary part of the brain stem. ”

“ In the front part of the head are two organs, which appear to supplement, in some remarkable way, probably by touch-sensations, the power of vision, and also to possess other capabilities constituting a sense to which we have nothing strictly analogous. These organs are called antennæ. They spring from origins near together, at equal distances from the medial and anterior point of the head, and are connected, by distinct and somewhat large filaments, with the nerve matter forming the cephalic ganglia. ”

“ We are told, and with perfect truth, that in man the occipital foramen--the aperture through which the brain is connected with the spinal cord--is so placed that the head is nearly in equilibrium when he stands upright. ”

“ This cord connects the brain with the various parts of the body. There is a soft cushion of cartilage between each spine, which adds much to the elasticity of the back-bone, protecting the brain from shocks. This protection is further accomplished by the curvature of the spine. These bones are not placed directly over each other, but are so arranged as to give three curves to the spinal column. Along the column there are openings, at each joint, through which the nerves come to supply fibers to the different organs of the body. ”

“ Is the Brain which is preserv'd in the Skull all of one Piece, or one equal Mass?
No, it is distinguish'd by the means of the Meninges into the Brain it self, and the Cerebellum or little Brain; the Brain, properly so called, takes up almost the whole Cavity of the Skull, and the Cerebellum is lodg'd altogether in the hinder-part, where it constitutes only one entire Body; whereas the former is divided into the Right and Left Parts by the Meninges, which cut it even to the bottom; whence these Foldings are call'd Falx ”

“ It has also to serve as a passageway for thousands of delicate gossamer-like nerve fibres passing from the brain, which fills the whole chamber of the skull, to the spinal cord, situated in the canal of the backbone. By means of these delicate fibres the brain dispatches messages which control the muscular engines of the limbs and trunk. ”

“ The brain occupying the cranial cavity and the spinal cord in the spinal cavity connect with each other through the large opening at the base of the skull to form one continuous structure. The brain and cord are the most complicated portions of the nervous system, and the ones most difficult to understand. ”

“ In other words, there is every reason to believe that numerous "centres," in this restricted sense, exist in the brain that have as yet eluded the investigator. Indeed, the current conception regards the entire cerebral cortex as chiefly composed of centres of ultimate co-ordination of impressions, which in their cruder form are received by more primitive nervous tissues—the basal ganglia, the cerebellum and medulla, and the spinal cord.
This, of course, is equivalent to postulating the cerebral cortex as the exclusive seat of higher intellection. ”