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Updated: June 2, 2025
I. The various organs of sense require various kinds of stimulation to excite them into action; the particles of light penetrate the cornea and humours of the eye, and then irritate the naked retina; rapid particles, dissolved or diffused in water or saliva, and odorous ones, mixed or combined with the air, irritate the extremities of the nerves of taste and smell; which either penetrate, or are expanded on the membranes of the tongue and nostrils; the auditory nerves are stimulated by the vibrations of the atmosphere communicated by means of the tympanum and of the fluid, whether of air or of water, behind it; and the nerves of touch by the hardness of surrounding bodies, though the cuticle is interposed between these bodies and the medulla of the nerve.
When these intermittences are regular, perhaps two beats to one intermittence, or three beats to one intermittence are the most frequent types. When the auricles also beat slowly, perhaps the vagiare for some reason overstimulated and thus inhibit the heart's activity. The attacks of syncope are doubtless due to anemia of the medulla, because of the infrequent ventricular contractions.
The centre of the joint was selected because when a lever is set in motion the part at the fulcrum moves least, and the medulla, being placed at that point, is least exposed to disturbance when we bend our heads backwards, forwards, or from side to side.
The Medulla Oblongata is the upper enlarged end of the spinal cord, and from it and the Cerebrum branch forth the Cranial Nerves which reach to various parts of the head, to the organs of special sense, and to some of the thoracic and abdominal organs, and to the organs of respiration. The Spinal Cord, or spinal marrow, fills the spinal canal in the vertebral column, or "backbone."
II. The following article evinces that the organ of vision consists of a fibrous part as well as of the nervous medulla, like other white muscles; and hence, as it resembles the muscular parts of the body in its structure, we may conclude, that it must resemble them in possessing a power of being excited into animal motion.
The SECOND is that of RESPIRATION: like volition, the motive influence in respiration passes in a DIRECT LINE from one point of the nervous system to certain muscles; but as voluntary motion seems to originate in the cerebrum, so the respiratory motions originate in the medulla oblongata: like the voluntary motions, the motions of respirations are spontaneous; they continue, at least, after the eighth pair of nerves have been divided.
"Broken as a man's neck is broken by hanging dislocation, really the disjointing of the medulla oblongata, if you don't mind technicalities," he said. "But I kept him living just the same. Time enough for him to repent in and get ready to go. A most interesting case. He was a criminal, too, and wanted to die; but you have to keep life going if you can, to the last inch of resistance."
MacDonald offers as a physiologic explanation of this case that probably the impression produced forty-two years before implicated the right brachial plexus and the afferent branches of the pneumogastric, and to some degree the vomiting center in the medulla; hence, when the atmosphere was highly charged with electricity the structures affected became more readily impressed.
In creating a movable joint for the head, then, a safe passage had to be obtained for the medulla that part of the great nerve stem which joins the brain to the spinal cord. 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 four long years my brother had suffered from a weakness of all the muscles, which made me always fear that the seat of the trouble was the medulla oblongata. Yet his step was firm; his head was entirely clear. The higher intellectual faculties retained all their energy.
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