Medulla oblongata

“ While the power of motion in each part seems thus to be dependent on isolated points of the medulla oblongata and the medulla spinalis, an indirect or connecting influence is admitted to take place between them and the remaining parts of the brain; and whatever may be its nature or extent in animals, there can be no doubt of its being so infinitely greater in man as to be essentially different ”

“ Another part forms the medulla oblongata, that important hind brain in which lie so many of the vital centres of nervous energy. The central cavity formed by these constrictions is of comparatively less importance, forming ultimately what is known as the mid-brain. The foremost or anterior vesicle, however, is of the very greatest importance, and its subsequent changes are more marked than either of the other two. ”

“ When they are excited, these muscles contract and the size of the arteries is diminished: when they are paralyzed, the arterial inner muscles relax and the vessels dilate. The vaso-motor nerves have their governing centre in that upper portion of the spinal cord which is within the skull, the so-called medulla oblongata. When the spinal cord is divided, the vessels are cut off from the influence of this vaso-motor centre, and at once dilate, profoundly affecting the blood-current by doing so. ”

“ After the removal of the brain from the skull the abnormal dimensions of the cerebrum present a remarkable contrast to the normal size of the cerebellum, pons, and medulla oblongata, which also appear flat and broad from pressure. When a horizontal section is made through the hemispheres of the cerebrum and a little above the corpus callosum, the centrum ovale appears unusually large. The cavities of the ventricles are very narrow, their walls touching one another. There is no serum in the pia mater or in the ventricles. The substance of the brain is pale, bloodless, and dry. ”

“ In many cases, as has been remarked before, the pathological process descends into the spinal cord. Here, as in the medulla oblongata, the degeneration is principally confined to the motor centres located in the anterior horns, while the posterior horns, together with the lateral and posterior white columns, remain free from disease. The degree of degeneration taking place in the fibres of the respectively paralyzed muscles also corresponds to that of the elements of the nerve-centres from which they are supplied. ”

“ In nearly every case stimulation of the peripheral end of the cut splanchnic at the point where it passes through the diaphragm causes contraction of both kidneys; the kidney of the side opposite to the nerve stimulated commencing to contract later than the one on the same side as the stimulated nerve.
“11. Stimulation of the central end of a sensory nerve, or of the medulla oblongata, or of the cervical spinal cord, causes a contraction of the renal vessels after both splanchnics have been cut at their point of entrance into the abdominal cavity. ”

“ 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. ”

“ The head had to be balanced in such a way that through the pivot or joint on which it rests a safe passageway could be secured for one of the most delicate and most important of all the parts or structures of the human machine. We have never found a good English name for this structure, so we use its clumsy Latin one—Medulla oblongata—or medulla for short. In the medulla are placed offices or centres which regulate the vital operations carried on by the heart and by the lungs. ”

“ In the course of these studies Flourens discovered that in the medulla oblongata, the part of the brain which connects that organ with the spinal cord, there is a centre of minute size which cannot be injured in the least without causing the instant death of the animal operated upon. ”

“ On the closure of the medullary groove the lumen of the medullary canal is continued uninterruptedly through the brain, but dilates considerably in each of the cerebral vesicles.
The anterior lobe of the brain becomes converted into the cerebral hemispheres, the thalamencephalon, the primary optic vesicles, and the parts connected with them. The middle lobe becomes the optic lobes (corpora bigemina or corpora quadrigemina in Mammalia) and the crura cerebri; while the posterior lobe becomes converted into the cerebellum and medulla oblongata. ”

“ But though the heart muscle is no doubt participating in the general paresis, the condition of the surface of the body is in reality one of anæmia. The blood, even at this early stage, begins to accumulate in the large veins of the abdomen, which expand gradually in consequence of the diminishing [Pg 22] motor force supplied by the splanchnicus, keeping them in the normal state of contraction when intact and having its centre in the medulla oblongata. When this large vaso-motor nerve is cut in animals anywhere in its course, the veins of the abdomen become distended enormously. ”

“ In other cases there are lesions of the medulla oblongata, or of the vagus or glossopharyngeal nerves or their œsophagean branches.
Death usually results from obstruction, inanition, or, in case the paralysis is partial, from pneumonia or exhaustion.
Treatment. First remove or correct the existing cause of the disease. Impaction may be broken up by the use of the wire loop, or pincer probang; parasites may be expelled by passing a cupped probang; the impactions following arytenectomy can be obviated by feeding gruels, milk and other liquid foods only, and from a bucket set on the ground ”

“ The embryos may develop in the medulla oblongata as well as on the brain itself. Compression and atrophy of the medulla then give rise to true paralysis.
The animals exhibit paralysis of the hind quarters, unilateral paralysis 473only, or still less marked signs. Everything depends on the degree of development of the cysts.
Bovine Animals. Cœnurosis in oxen is less important than in sheep. Moreover, it very rarely affects a large number of young animals belonging to one farm. Loss of appetite, dulness and depression are the earliest indications, as in sheep. ”

“ Yellow matter beneath arachnoid along course of vessels on each side of anterior lobes. Abundant fine granulations along course of vessels on each anterior lobe, on upper margins of median fissure, along fissure of Sylvius, and on choroid plexuses. Very little lymph at base of brain. Six or eight ounces of serum from lateral ventricles, and abundant fine transparent granules over ependyma of both. Numerous opaque granulations in pia mater of medulla oblongata. Surface of right pleura universally adherent. ”

“ Sometimes there is no rallying, death following the injury immediately. In cases where there is no reaction, the patient gradually becomes weaker, and his pulse feebler, till death ensues. Shock is due to an impression conveyed to the medulla oblongata, by which the nerve-centres are so affected that a partial paralysis of the voluntary and involuntary muscular fibres in the body takes place, the patient being, perhaps, unable to lift his arm or move his leg. ”

“ If the cerebellum and cerebrum of a dove be removed, the bird will make no effort to procure food, but if a crumb of bread be placed in its bill, it is swallowed naturally and without any special effort. So also in respiration the lungs continue to act after the intercostal muscles are paralyzed; if the diaphragm loses its power, suffocation is the result, but there is still a convulsive movement of the lungs for sometime, indicating the continued action of the medulla oblongata. ”

“ The medulla is a center for the movements of chewing and swallowing. This center can be excited in a reflex manner, and by the will, but not automatically. There seems to be good evidence that the medulla is a center for combined or co-ordinated movements of the body. Wundt is of opinion that the collective motor-fibers of the body are brought into closer union with each other in this organ. His opinion rests upon the fact that, as long as the medulla is intact, sensible excitations occasion general movements of the body much more easily than when this organ is destroyed. ”

“ In this double experiment, the nerves remain attached to the membrane separated from its medullary substance, because their nervous coat is continued with it. It is exactly as if a number of small arterial filaments went from the aorta; the parietes of this artery would be to those of these filaments, what the pia mater of the spinal marrow is to the coat of the nerves which go from it. Only the nerves are white, because their medulla fills them; whereas the canal to which they belong is transparent, because it is deprived of its own medulla. ”

“ The adrenal or suprarenal gland lies just above the kidney, and anatomically has two parts, an outer cortex or shell, and an inner medulla or pulp. The medulla gives off adrenalin, which regulates blood pressure in all parts of the body through action on the blood vessels. The cortex gives off an unknown secretion which seems to have a remarkable influence. When it is diseased, certain curious things happen. ”

“ The kidney in the foetus is lobulated, but the intervals between the lobes become smoothed out in later years of childhood. Each gland is invested the renal artery from the aorta passes. Here also the renal vein escapes and joins the vena cava inferior. The ureter or metanephric duct, always behind and below the blood vessels, emerges here and passes downward to the bladder. When the kidney is longitudinally divided from hilum to outer edge, the cut surface is seen to consist of two parts-an outer layer, the cortex, and an inner part, the medulla (fig. 1) . ”

“ From the First to the Third Day.—The period of inflammation and exudation. Ordinary signs of inflammation and laceration of the parts. Blood will be found extravasated round the fracture, also in the medullary canal mixed up with the fat.
From the Third to the Fourteenth Day.—Gradual subsidence of inflammatory action and growth of the soft provisional callus from the periosteum and surrounding structures, and internally in the medulla, forming a fusiform mass holding the broken ends of the bones together with some degree of firmness. This becomes firmer and almost cartilaginous in density. ”

“ There is a respiratory circulation, the contractile ventral vessel which represents the heart sending the colourless blood forward to the respiratory pharynx to be purified. The body-wall is segmented into over fifty myotomes. There are numerous separate nephridia which develop from the mesoderm and open into the atrium. The brain remains undeveloped, being scarcely distinct from the spinal cord. There are two pairs of cerebral nerves, and many spinal, in which the dorsal and ventral roots or nerves do not unite. The sense-organs are simple; there are no paired eyes and no auditory organs. ”

“ Although a centre has been thought to exist controlling the circulation in the lungs, whose paralysis has been supposed to explain the occurrence of sudden pulmonary œdema without other known cause, no definite facts regarding it are known. That the action of the heart is under the control of the medulla is a fact too well known to require more than a mention. ”

“ Complete muscular resolution is most common when the effusion is bilateral, but when the hemorrhage is limited to one side more or less paralysis of the opposite limbs may exist. Should the blood make its way into the spinal canal, it might give rise to special symptoms, but this is not probable in view of the large amount of the cerebral effusion under the circumstances, which would produce complete insensibility or speedily cause death by pressure on the medulla. ”

“ The medulla forms a dark line passing along the centre of the hair, and occupies about a fourth or a fifth of its thickness. The medullary line is absent in infants’ hair, and in very fine light hair; it is present in strong hair, and is not difficult 7to trace in white or grey hair. Dr. Beigel observes, that “we may drive out the air contained in the central tube—as the medullary has likewise been called—and see it re-enter again under the microscope. Turpentine penetrates all parts of the hair which are filled by air, but its action is slow and requires some time. ”

“ The periosteum becomes inflamed; a widespread suppurative periostitis is the result; necrosis of the bone from insufficient nutrition follows, while mechanical pressure on the pus aids in its absorption. The medulla frequently takes on suppurative inflammation, and here the surgeon fails to receive prompt warning of danger; slowly the suppuration progresses, without pain or other symptoms unless the disease has extended to the other tissues; the medullary cavity at the fractured end of the bone may be completely or partially occluded by a new osseous formation ”

“ On each side of the œsophagus, in close relation with the anterior cardinal vein (ac) , is noticed a nerve (cn) cut through a ganglionic enlargement. When traced forward these nerves are seen to arise from the region of the medulla, and when followed caudad they are found to be distributed chiefly to the tissues surrounding the newly formed bronchi; they are doubtless the tenth cranial nerves. On the right side of the figure the close connection of this nerve with the near-by gill cleft is seen. ”