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Clinically, the osteoma forms a hard, indolent tumour attached to a bone. The symptoms to which it gives rise depend on its situation. In the vicinity of a joint, it may interfere with movement; on the medial side of the knee it may incapacitate the patient from riding. It incapacitates the patient from wearing a boot. When it presses on a nerve-trunk it causes pains and cramps.

The uninjured nerve-bundles continue to transmit impulses with the result that there is a dissociated paralysis within the distribution of the affected nerve, some muscles continuing to act and to respond normally to electric stimulation, while others behave as if the whole nerve-trunk had been severed.

#Anatomy.# A nerve-trunk is made up of a variable number of bundles of nerve fibres surrounded and supported by a framework of connective tissue. The nerve fibres are chiefly of the medullated type, and they run without interruption from a nerve cell or neuron in the brain or spinal medulla to their peripheral terminations in muscle, skin, and secretory glands.

If pain is a part of a muscular response and occurs only as a result of contact ceptor stimulation by physical injury, infection, anemia, or obstruction, we may well inquire which part of the nerve mechanism is the site of the phenomenon of pain. Is it the nerve-ending, the nerve-trunk, or the brain?

That is, is pain associated with the physical contact with the nerve-ending, or with the physical act of transmission along the nerve-trunk, or with the change of brain-cell substance by means of which the motor-producing energy is released? We postulate that the pain is associated with the discharge of energy from the brain-cells.

Whether it acts by merely setting up some trophic change in the nerve-tissue, or by tearing loose inflammatory adhesions which are binding down the nerve-trunk, the procedure gives excellent results, nearly always temporary relief, and sometimes a permanent cure.

On the other hand, excessive pressure, except when applied directly over some nerve-trunk, tends to excite more discomfort than pain." The confusion between discomfort and pain has made people regard discomfort as a more substantial thing than it is, and this in turn has reacted upon the view taken of pleasure, since discomfort and pleasure are evidently on a level in this respect.

The connective-tissue framework of a nerve-trunk consists of the perineurium, or general sheath, which surrounds all the bundles; the epineurium, surrounding individual groups of bundles; and the endoneurium, a delicate connective tissue separating the individual nerve fibres. The blood vessels and lymphatics run in these connective-tissue sheaths.

This lowering of temperature under the influence of a powerful irritation of a nerve-trunk or of its minute branches, which everywhere pervade the tissues and spread out in the skin, is common to all species of mammals. If a rabbit be merely tied down tightly upon a table, the fall is perceptible, and if it be severely wounded, the temperature diminishes very greatly.

From the fact that it projects from the surface of the bone it is often spoken of as an exostosis. It grows slowly, and rarely causes any discomfort unless it presses upon a nerve-trunk or upon a bursa which has developed over it. Operative interference is only indicated when the tumour is giving rise to inconvenience. It is then removed, its base or neck being divided by means of the chisel.