Corpus callosum

“ Deformity and deficiency of the corpus callosum in some degenerates is but an expression of general defect of associating tracts. Convolutional aberration in others is but an expression of imperfect development of end stations and fibre systems. All mental and moral disturbances are associated with perversions of the functions of the cerebral hemisphere, but the converse, that cerebral hemisphere lesions only are the essential accompaniments of mental symptoms evinced during life, is not true. ”

“ After the removal of the dura mater, a small segment of cerebellar surface became visible on each side, posteriorly to the tips of the occipital lobes. It is well known [3] that the anteroposterior dimensions of the corpus callosum are very different in a brain whilst contained and supported within its case, and when removed from the skull,—the forward swaying of the hemispheres upon their supporting stems, the crura, flattening the previously arched commissure. ”

“ Let us take an organ for example in each of the two lives. I have always seen that in a small brain the corpus callosum, the thalami nervorum opticorum, the corpora striata, &c. are in proportion to the whole size of the organ. ”

“ A general idea of the internal structure of the brain is best obtained by studying a horizontal section made just below the level of the Sylvian point and just above the great transverse fissure (see fig. 14) . Such a section will cut the corpus callosum anteriorly at the genu and posteriorly at the splenium, but the body is above the plane of section. Behind the genu the fifth ventricle is cut, and behind that the two pillars of the fornix which here form the anterior boundary of the third ventricle. ”

“ Cruveilhier cites a case of a girl of eleven who had absolutely no cerebellum, with the same symptoms which are characteristic in such cases. There is also recorded the history of a man who was deficient in the corpus callosum; at the age of sixty-two, though of feeble intelligence, he presented no signs of nervous disorder. Claude Bernard made an autopsy on a woman who had no trace of olfactory lobes, and after a minute inquiry into her life he found that her sense of smell had been good despite her deficiency. ”

“ To it belong not only the large hemispheres, but also the corpus callosum that unites them, the olfactory lobes, from which the olfactory nerves start, and most of the structures that are found at the roof and bottom of the large lateral ventricles inside the two hemispheres, such as the corpora striata. ”

“ The latter regarded the convoluted surface of the cerebrum as the seat of the memory and the will, the convolutions being intended to retain the animal spirits for the various acts of imagination and memory. Imagination he described as seated in the corpus callosum, sense-perception in the corpus striatum, and impetus et perturbatio in the basal parts of the cerebrum above the crura. The thalami he regarded as the centres of sight and the cerebellum of involuntary acts. Succeeding anatomists simply varied these localizations according to their respective fancies. ”

“ When the surface of the human brain is inspected, it is seen to present a very unequal appearance, due to the fact that its substance is thrown into a large number of folds or convolutions (see Fig. 1) , as they are technically named by the anatomist. The brain, or cerebrum, is in reality a double organ, formed of two similar halves or hemispheres, which are separated by a deep central fissure, but which are also connected together below by a broad band of nervous matter known as the corpus callosum. ”

“ Fishes have two-chambered hearts; frogs and most reptiles have three-chambered hearts; all mammals and birds have four-chambered hearts. The red corpuscles in the blood of fishes, frogs, reptiles, and birds, are discs, double-convex, nucleated, and in shape oval or triangular. In man and in all other mammals (except the archaic camel) the red corpuscles are double-concave, non-nucleated, and circular. ‘Man has a diaphragm dividing the body cavity into chest and abdomen, and a shining white bridge of interlacing fibres, called corpus callosum, uniting his cerebral hemispheres. ”

“ The human blood-corpuscle is a non-nucleated, biconcave disc, having a diameter of about 1/3500 of an inch. All mammalian red corpuscles have the same shape, except those of the camel, which are oval. The corpuscles of birds, fishes, reptiles, and amphibians, are oval and nucleated. The corpuscles of most mammals are smaller than those of man, but the size of a corpuscle is affected by various circumstances, such as drying or moisture, so that the medical witness is rarely justified in going farther than stating whether the stain is that of the blood of a mammal or not. ”

“ The corpuscles are very flexible and can squeeze through small apertures, as in the tiny capillaries, and regain their shape. They are probably formed chiefly in the red bone marrow at the ends of the bones, which under the microscope shows red corpuscles in various stages of growth, and also in the spleen, for which no other use is known. Their function is to carry oxygen, which forms a chemical combination, though an extremely loose one, with the hemoglobin. As the tissues are more greedy of oxygen than is the hemoglobin, they rob the corpuscles of it. ”

“ Callosities are prominent, indurated masses of the horny layer of the epidermis, where it has been exposed to prolonged friction and pressure. They occur on the fingers and hand as a result of certain occupations and sports, but are most common under the balls of the toes or heel. A bursa may form beneath a callosity, and if it becomes inflamed may cause considerable suffering; if suppuration ensues, a sinus may form, resembling a perforating ulcer of the foot. ”

“ It suffices that the white corpuscles or leucocytes, retaining the primitive amœboid character, exhibit individual activities: send out prolongations like pseudopodia, take in organic particles as food, and are independently locomotive. Though far less numerous than the red corpuscles, yet, as ten thousand are contained in a cubic millimetre of blood—a mass less than a pin's head—it results that the human body is pervaded throughout all its blood-vessels by billions of these separately living units. ”

“ In the human species the red corpuscles are thick and circular. They are so small that Young says it would take 255,000 of them to cover a surface of a square inch. They are elastic and pliant, so that they can pass through blood vessels having a smaller diameter than themselves. The white corpuscles are more globular than the red, and contain more fat, and have the power of changing their form. ”

“ What first suggests itself is that the gland cells themselves are made to contract rhythmically by the various conditions which cause rhythmical contractions in muscle. That the stimulus for this must be greater in the case of secretion is shown by the fact that in the intestine peristaltic movements may be maintained in a solution (m/6 NaCl) in which no secretion takes place. It seems not at all improbable that one factor in the production of secretory activity is dependent on a property of the gland cell closely related to muscular contractility. ”

“ At the end of about three weeks, if you make a section of the callus, minute specks of earthy matter are visible, deposited in it here and there, and at the same time some of the callus, appears to disappear on the outside, so that the neighboring muscles and tendons no longer adhere to it. The specks of bone become larger and more numerous until they extend into each other; and thus by degrees the whole of the callus is converted into bone. ”

“ But we have also seen that the cambium is not the only living tissue below the bark: the cortical parenchyma (pa) and the cells (c) of the inner cortex (technically the phloem) are all living and capable of growth and division, as was described above. The release from pressure affects them also; in fact, the "callus," or cushion of tissue which starts from the lips of the wound and closes it over, simply consists of the rapidly growing and dividing cells of this cortex, i.e., the release from pressure enables them to more than catch up the enlarging layer of cortex around the wound. ”

“ If it is larger, the amount of fluid lost is first made up by fluid drawn from the tissues, so that the number of corpuscles is apparently diminished by dilution of the blood; the erythroblasts, or formative red corpuscles, of the bone-marrow are stimulated to proliferation, and new corpuscles are quickly thrown into the circulation. ”

“ As already stated, there is every reason to conclude that the right cavities of the heart are distended with blood, in all cases of suspended animation by chloroform, and therefore it would be desirable to open one of the jugular veins if the artificial respiration does not immediately restore the patient. In opening animals, just after death from this agent, I have observed the contractions of the heart to return, to a certain extent, when the distension of its right cavities was diminished by the division of the vessels about the root of the neck. ”

“ The method then [477] of breaking them over again is not at all to be admitted, as it may occasion the utmost danger; but if the callus be newly formed, we must have recourse to the allusions of a relaxing nature, and to cataplasms, such as those from fat olives and pigeon’s dung, and the other medicines for dissolving callus; and we also dispel it by friction with the hand, and bending it every way. But if it be of a stony hardness, we make an incision of the skin with a scalpel, and separate the union of the bones with chisels, and then cure the fracture as formerly said. ”

“ The chief part of the nervous system is the ventral nerve-chain, which runs along the under-side of the body. This is a long cord having at intervals a series of knots or swellings, the ganglia or nerve-centres, from which nerves are given off to the appendages and to the organs of the body. In the hinder part of the thorax and in the abdomen there is a ganglion in each somite, but in front these ganglia become crowded together and coalesced, so that we find only a single large ganglion, corresponding to the somites from that of the mandibles to that of the third maxillipeds. ”

“ The removal of these glands in animals produces a condition resembling acute poisoning accompanied by spasmodic contraction of the muscles. A small glandular organ at the base of the brain, the pituitary body, produces a secretion, one of the most marked properties of which is a control of growth, particularly that of the bones. Most cases of giantism, combined as they are with imperfect mentality, are due to disease of this gland. There are glands near the kidney which regulate the pressure of the blood in the arteries by causing contraction of their muscular walls. ”

“ The co-operation of the brain with the nerves is, of course, necessary to sensation; and it is possible by a large dose of chloroform to produce complete anæsthesia very suddenly, before there is time for the nerves to be acted on locally to any extent; and if the chloroform is not continued, the anæsthesia may subside as quickly as it was induced. ”

“ The white corpuscles are in reality embryonic structures, concerned chiefly in the production of other forms, such as red corpuscles, and it may be under certain conditions various elements of the other tissues. The red corpuscles have a definite respiratory function. But these form a part only of the blood. The largest portion of the blood, the whole mass of the plasma, is an unorganized fluid with no proper physiological (vital) properties of its own. Its function is to serve as the great medium of exchange between all the tissues of the body. ”

“ As the above experiments clearly show, splanchnic stimulation on the glandless side results in no shortening of the coagulation time; whereas, in the same animals, stimulation of the nerves on [p. 170] the other side (still connected with the adrenal gland) produces a sharp hastening of the clotting process.
The splanchnics innervate the intestines and liver even though the adrenal gland is removed. The foregoing experiments indicate that the nerve impulses delivered to these organs do not influence them in any direct manner to accelerate the speed of coagulation. ”

“ It is generally believed that the red corpuscles are derived in some way from the colorless. It is supposed that the red corpuscle is merely the nucleus of a colorless corpuscle enlarged, flattened, colored and liberated by the bursting of the wall of its cell. When blood is taken from an artery and allowed to remain at rest, it separates into two parts: a solid mass, called the clot, largely composed of fibrin; and a fluid known as the serum, in which [pg 55] the clot is suspended. ”

“ As the corpuscles grow older and become more rigid, they, as it were, are caught by the amœboid cells. As cells containing blood corpuscles are very rarely found in the general circulation, one may assume that the occurrence of these cells within the spleen, liver, and marrow of bone, is favored by the slowness of the circulation in these organs. ”

“ So many unknown conditions exist in such an organ that it is impossible to say what tissue is acted on primarily, whether the nervous system on the one hand, or the glandular and muscular tissues on the other. There are, however, two indicators in the intestine by which the comparative actions of substances can be studied, namely, the muscular movements, and the secretion of fluid, both of which by various chemical substances may be increased or lessened ”

“ Under a microscope you will see a number of little round bodies—the blood-discs, or blood-corpuscles. All the redness there is in blood belongs to these. These red corpuscles are not hard, solid things, but delicate and soft, yet made to bear all the squeezing they get as they drive around the body. Besides these red corpuscles, are other little bodies, just a little larger than the red, not colored at all, and quite round. These are all that one can see in blood, but it has a strange property which we will study. Whenever blood is shed from a living body, within a short time it becomes solid. ”