Reflex Tonic Spasm of muscles around a diseased or dislocated joint, or of those controlling its action, often affords a valuable means of diagnosis, the possibility of nervous, muscular and tendinous disease being excluded.
TROPHIC SYMPTOMS AND DISORDERS.
Degenerative atrophy, in hæmoglobinuria, laryngeal hemiplegia, neurectomy, nerve lesion, brain or cord lesion, lead poisoning, disuse. Dermatitis, ulceration, morbid secretion, polyuria, mellituria, albuminuria, poisonous milk.
Degenerative Atrophy. From section, disease, atrophy or degeneration of nerves or nerve centres, the muscles, which they normally innervate, waste, often to an extreme degree. As examples of this we see the atrophy of the triceps extensor cruris and other groups in hæmoglobinuria, of the intrinsic laryngeal muscles in roaring, of the muscles supplied in neurectomy, and of groups of muscles in myelitis, broken back, lead paralysis, and scapular muscular atrophy. True to the law of wasting of physiologically inert organs, the nerves are atrophied and degenerated, and often also the bones, joints and skin.
The degeneration of an active organ applies to the nervous tissues themselves. According to the law of Waller, the nerve fibre (axis cylinder), when cut off from its nutritive centre (cell body with nucleus) degenerates and ultimately perishes. The axis cylinder is a component part of the neuron, which includes also its continuation in the cell and nucleus, and when the latter, which is the source and origin of both nerve impulse and trophic control, is lost, the inactive axis of the nerve fibre degenerates. This law is now availed of in tracing the distribution of nerve filaments, the degeneration being found in those that have been cut off from their nerve cells while those that come into the nerve trunk from other sources, distal of the injury, maintain their integrity.
In addition to this peripheral atrophy, a degeneration central of the injury to the nerve is seen under certain conditions, but especially in intrauterine life. In such cases the atrophy may extend up to and include the central nerve cells, causing a secondary central nervous lesion from an initial peripheral one.
By bearing these laws of nerve atrophy in mind, lesions that would otherwise be obscure, may be satisfactorily accounted for.
Eruptions and Ulcerations of Nervous Origin. Herpes or shingles in man is now recognized as a nervous disease, circumscribed to the distribution of given nerves and occurring unilaterally or bilaterally. Deep-seated dermatitis, vesicles, neuralgia, pain, itching and formication are common accompaniments. The whole is traced to disease of the ganglion on the posterior (superior) root of the spinal nerve distributed to the part. This establishes a principle, and in inscrutable and obstinate, circumscribed skin disease the veterinarian should see if it coincides with the distribution of one or more sensory spinal nerves.
Ulcerations are often caused by the lack of protection of a part after paralysis, thus perforation of the cornea will follow section or disease of the trigeminus. These may be prevented by carefully covering the part, and even cured by a fine protective covering like collodion.
Alteration of the Secretions often follow on section of the sympathetic trunks, that of the cervical sympathetic in rabbits causing excessive congestion of the facial skin, with exudation and scabby product, also profuse secretion of sweat, tears, and ear cerumen and dry, scaly skin.