in the less intelligent species, and in wolves, they exist in a much inferior degree of developement. Every one must have been struck by the great difference as to docility observable between dogs and cats; an equally striking difference is found in the appearances presented by the number and depth of the convolutions of their brains-a difference so great, that Desmoulins estimates the convolutions of the dog to exceed by six or eight times those of the cat. The paucity of convolutions found in the cat prevails throughout the entire genus to which it belongs. That genus, Felis, which includes the cat, lion, tiger, panther, and other animals of a similar nature, is likewise remarkable for the uniformity observed in the number and arrangement of the convolutions in the different species; and in no genus are the species more distinguished for similarity of disposition, for through none do the faculties of Secretiveness and Destructiveness prevail in so extreme a degree of strength. It must also have struck every observer, that differences of mental character are met with to a much greater extent, and with much greater frequency, among men, than among the individuals of any species of the lower animals. It is rare, for instance, to find one sheep differing much from its companions, or one cow from another. This must, therefore, be regarded as a circumstance affording a presumption in favour of the idea that varieties of disposition depend on varieties occurring in the convolutions; since, as has been observed by various physiologists,* the brains of men vary, with respect to the number and depth of their convolutions, in a far greater degree than those of any other species. It has been remarked, that, in most idiots, the number and depth of the convolutions are less than usual, on at least one side of the brain. In chronic insanity, too, the convolutions are found more or less effaced, and separated from each other by the thickening and infiltration of the lamina of the pia mater occupying the furrows of the brain. In these cases, likewise, as well as in individuals of congenital imbecility, the thickness of the cineritious substance of the convolutions has been found greatly diminished; while in acute mania, on the other hand, it has been found of the usual thickness, and highly injected with blood. In old age the convolutions shrink. The greater part of the brain is destitute of sensibility: it may be pierced or cut without the patient being aware, from any feeling of pain, that it is suffering injury. Sir Charles Bell mentions, that he "had his finger deep in the anterior lobes of the brain, when the patient, being at the same time acutely sensible, and capable of expressing himself, complained only of the integument." So far from thinking the parts of the brain which are insensible to be parts inferior in function, (as every part has its use,) Sir Charles Bell states, that, even from this, he should be led to imagine that they have a higher office, namely, that they are more allied to intellectual operations. The wide difference of function between a part destined to receive impressions, and a part which is the seat of thought, is in accordance with the presence of sensibility in some parts of the brain, and its absence in others. The brain receives an unusually large supply of blood, in comparison with the rest of the body. According to Haller, the quantity is one-fifth of the entire amount which leaves the heart; Monro, however, estimates it at one-tenth. Each side of the brain, and also the cerebellum, are supplied with separate arteries conveying the blood to them; but the sinuses, or canals by means of which the blood is returned to the heart, are common to them all. The CEREBELLUM is composed of the same kind of nervous matter with * Vicq d'Azyr, Mém. de Paris, 1783, p. 512; cited by Meckel, Anatomie, &c., vol. ii., p. 646. See also Wenzel, De penitiori Structura Cerebri, p. 23, and Mayo's Physiology. the brain, and presents both cineritious and medullary substances; but it differs from it in form and internal arrangement. In fig. 3, p. 75, it is seen partly in section (between S and 48) and partly with its natural external appearance (1.) The cerebellum is separated from the brain by a strong membrane called the tentorium: in animals which leap, as the cat and tiger, the separation is produced by a thin plate of bone.* Its fibres, however, originate in that part of the medulla oblongata called the corpora restiformia, from which also the organs of several propensities arise; so that the brain and cerebellum, although separated by the tentorium, are both connected with the medulla oblongata, and through it with each other. The MEDULLA OBLONGATA is sometimes spoken of as one of the three great divisions of the brain. It is, in fact, the part from which the fibrous matter of the brain and cerebellum proceeds; and it forms, as it were, the capital of the column of the spinal marrow. OF THE INTEGUMENTS OF THE BRAIN. THE brain is formed before the bones which invest it. The ossification of the skull is a gradual process. The brain already formed is invested with strong membranes, and between the coats of the outer membrane the ossification commences, which process is not completed until the ninth year. During life the brain is embraced in its whole peripheral extent by a very thin transparent and delicate membrane called the pia mater, which sinks down into its furrows, and serves to convey the blood vessels to its different parts. Immediately above the pia maler are two layers of a still thinner membrane, resembling in its tenuity a spider's web, and thence named the tunica arachnoidea. It covers the surface of the brain uniformly, without passing into its folds. A fluid secretion takes place from the opposed surfaces of this membrane, by which they are lubricated and prevented from adhering to each other. The dura mater is a thin, but strong, opaque membrane, lining and strongly adhering to the inner surface of the skull, and which embraces the outer surface of the brain above the membrane last-mentioned. When in health it does not possess sensibility, and has been pricked without causing pain. The brain, enclosed in these membranes, fills exactly the interior of the skull; so that a cast, in plaster, of the interior of the skull is a fac simile of the brain, covered by the dura mater. Between the two layers of the arachnoid membrane a very small quantity of fluid is said to exist, but not exceeding a line in thickness. This fluid does not, in any degree that can be distinguished by the hand or eye, cause the form of the interior of the skull to differ from the form of the exterior of the brain. The skull is not an adamantine barrier, confining the brain within specific boundaries; but a strong, yet changeable, covering, shielding it, and accommodating itself to its size while in the progress of its growth.† At birth it is small; it increases as the brain increases, and alters its shape with every change of the cerebral form; it stops in developement when the brain has attained its full size, and diminishes when the size of the brain suffers diminution, as happens in old age or disease. A process of ab Richerand conceives the purpose of this arrangement to be the prevention of cerebral concussion in leaping: but Dr. Vimont objects to this view, on the ground that many animals accustomed to take great leaps, such as the squirrel and monkey, have not an osseous tentorium; while, on the other hand, a bony plate occurs in some animals whose movements are slow and heavy, such as the badger. Vimont's Treatise on Human and Comparative Phrenology, i., 63. On the admirable fituess of the skull to protect the brain, see The Phrenological Journal, viii., 332. Cases of diminution of the skull will be found in The Phrenological Journal, ix., 468-470. sorption and deposition goes continually on in its substance; so that, if the brain presses from within, the renovating particles arrange themselves according to this pressure, and thus the figure of the skull and of the brain in general correspond. In cases of water in the head, the skull sometimes extends itself, by this process, to an enormous size. The skull is composed of nine bones. These are-two frontal bones, which compose the forehead, and generally soon unite into one, though in some adults they continue double; two parietal bones, forming the greater part of the upper and lateral regions of the skull; two temporal, around the ears; one sphenoid, in the anterior part of the basilar region; one occipital, in the back and under part of the skull, immediately above the neck; and one ethmoidal, at the base behind the nose. The lines of junction of these bones are termed sutures, and form, in most parts, a sort of dovetailing. The principal sutures are the sagittal, separating the two parietal bones at the middle of the top of the head; the coronal, which divides the frontal from the parietal bones; the lambdoidal, between the occipital bone and the two parietals, and deriving its name from its resemblance to the Greek letter lambda (A); the frontal, dividing the two frontal bones when they are not conjoined; and the temporal, named also the squamous, from its scaly appearance, dividing the temporal bones from the parietal, and to some extent from the sphenoid and occipital. B The annexed figure represents a skull with the two sides cut away, down nearly to the level of the eyebrow, leaving a narrow ridge in the middle of the top standing. AAA is the edge of the skull, resembling an arch. It is here represented thicker than it is in nature, in order to show the diploë. Most parts of the skull consist of two plates, called the outer and inner tables, having between them a spongy C substance, like cells in a marrow-bone, called the diploë. The substance hanging down from the arch of the skull, having delicate lines traced on it, like the sap-vessels in leaves, is the membrane which separates the two halves of the brain. It is a continuation of the dura mater, and is called the falciform process, from its resemblance to a scythe. It is well supplied with blood vessels; and a large portion of the blood returning from the brain to the heart, goes up these vessels into a canal formed by the membrane all along the line of its attachment to the skull. The course of the blood through the canal is from the front backward, and then downward. The two hemispheres of the brain are completely separated, as far as this membrane is seen to extend downward in the cut. At the lower edge of it an open space appears: the commissure, or collection of fibres which unite the two sides, named the corpus callosum, goes through that space. The cerebellum lies at B C, in a part of the skull not opened. The membrane, on reaching the point C, spreads out to the right and left, and runs forward, so as to separate the cerebellum from the brain; the latter lying above, and the former be low it. B is the mastoid process, or bone to which the sterno-mastoid muscle is attached. It lies immediately behind the opening of the ear, and is not connected with the brain. As the diploë, except in the parts mentioned below, is almost equally thick, it follows that the two tables of the skull are nearly parallel to each other. This is seen in the section represented in fig. 3, p. 75.* The internal, indeed, bears some slight impressions of blood vessels, glands, &c., which do not appear externally; but these are so small as not to interfere with phrenological observations. The departure from perfect parallelism, * See Dr. Caldwell on the parallelism of the tables, Phren. Journ., ix., 222. A. Basilar or Sphenoid Bone. Small portion reaching the surface at the side. B. Temporal Bone. C. Occipital Bone. D. Parietal Bone. E. Frontal Bone. M. Meatus Auditorius Externus, or external opening of the ear. P. Mastoid process of the Temporal Bone, which serves to give attachment to the Sterno SS. mastoid muscle. Sutures, or serrated edges by which the different bones are joined together. |