Part 2

=Pseudo-paralysis= occurs from muscular disease, injury, inflammation or degeneration and has no appreciable central nor nervous lesion nor anæsthesia.

=Spasm= (Hyperkinesis); abnormal violent muscular contractions with or without loss of consciousness.

=Tonic= (tetanic) =Spasm= is violent and continuous.

=Clonic Spasm= is rapidly intermittent:—Contractions and relaxations.

=Tremor= (trembling) consists in small, intermittent, involuntary contractions.

=Hemispasm= affects the face, or limbs, or both, on one side of the body and may precede hemiplegia.

=Monospasm= affects one limb, one group of muscles or a single muscle. It may be due to lesion of the brain, of the spinal cord or of the nerves. Thus it may imply commencing disease of the motor centres or tracts.

=Spasms of the Eyeballs= (rolling of globe to one side), and =Spasms of the Eyeballs and Head=, are important indications of apoplexy. They imply disorder (commencing irritation) of the cerebral motor areas. Advanced disease would probably determine hebetude, coma, drowsiness, or palsy. If epileptiform it turns away from the lesion. If hemiplegic it turns toward the lesion and away from the paralysis. If lesion of the pons it turns away from the lesion.

=Paraplegic Spasm= is a tonic spasm, partial in degree, causing stiff, tetanoid (spastic) walk. In all four extremities there may be mixed paresis and contraction. This often attends on hemorrhage into the meninges.

=General Spasms=, convulsions as in Eclampsia, Epilepsy, Chorea, Tetanus.

=Local Spasms= may be rhythmic or not, in slight cases to be seen only in the eyelids or superficial muscles as twitching, and occur in neurasthenia, or in poisoning by strychnia, brucia and other motor nerve poisons.

=Incoördination= (Dyskinesis) is the lack of the harmonious balanced movement of the various groups of muscles. Coördination of movement is due to a special mechanism in the spinal cord, and extending forward through the medulla oblongata, pons, and crura cerebri to the floor of the third ventricle. In the form of ataxia (lack of power of muscular control) it is usually the result of degeneration (sclerosis) of the superior columns of the cord, of the medulla, pons or crura. It may occur from degeneration or destructive change in the cerebellum, or from disease or section of the posterior roots of spinal nerves, or finally from the action of certain narcotic poisons (ptomaines, toxins).

=Staggering= (titubation) occurs from lesions of the cerebellum, medulla or pons; also from alcohol, opium, and other narcotics.

=Reflex Action.= The normal stimulation of different functions, motor, secretory, circulatory, etc., depends on the nerve centres in the spinal cord, which are roused into action by a centripetal impulse derived from a distant part. Thus the balanced contraction of the different muscles which preserves the equilibrium of the body, depends on the apprehension by the nerve centres, consciously or subconsciously, of such contractions (muscular sense), and it is largely under the control of the will. Here three impulses act coördinately: 1st, the afferent impulse from the muscle to the nerve centre; 2d, the efferent impulse from the nerve centre to the muscle; and 3d, the inhibitory or controlling, voluntary impulse from the sensorium to the nerve centre involved. In another case, savory odors, sapid flavors and masticatory movements cause a free secretion from the salivary glands. Again, the scratching of a dog’s breast causes him to move his hind limb as if he were himself doing the scratching. Again, the pricking of a limb causes the prompt, even if involuntary, contraction of its muscles to withdraw it from the source of irritation.

=Morbid Reflex.= Reflex action may be modified in various ways as the result of disease or injury. It may become excessive from irritability of the organ from which the centripetal impulse starts, or of the reflex centre in the spinal cord, or of the muscle or other organ to which the centrifugal impulse is directed, or, finally, from impairment of, or separation from the inhibitory centre in the cerebrum. It may be impaired or abolished from degeneration or destruction of any of the tissues just named, or of the conducting nerves which connect them to each other.

The contraction and closure of the pupil under light is a reflex act from the retina on the optic lobes, etc., and from these through the motor oculi to the iris. This reflex is lost and the iris fails to contract in: anæsthesia of the retina; atrophy of the optic nerve; disease of the optic lobe; superior (posterior) spinal sclerosis; disease of the motor oculi; or disease of the iris.

The lumbar reflex is lost in many febrile states in the horse, so that pinching of the loins fails to produce wincing, and this becomes a test of the active persistence of the disorder.

=Encreased Reflex= is often noticed when the parts, including the spinal reflex centre, are disconnected from the brain: as in lesions or disease of the cord in front (cephalad) of its reflex centre. Here the cerebral or voluntary inhibition is lost.

=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.