Part 3

=Polyuria= is determined by section of one point of the medulla behind the root of the vagus, mellituria by puncture between the vagus and auditory nerves (the hepatic vaso-motor centre), and albuminuria by a puncture in front of the latter. Impairment of the hepatic vaso-motor tracts in the spinal cord, or of the anterior or posterior cervical sympathetic ganglia, or of the first thoracic ganglion equally determines nervous mellituria.

=Poisonous milk= produced in hard worked mares, or over-excited dams of other species, causing dyspepsia, diarrhœa, arthritis or other trouble in the suckling, must be in part attributed to nervous disorder.

Practically all secretions and nutrition are largely under nervous control, so that modifications in quantity or quality can often be attributed to nervous influence.

SENSORY SYMPTOMS AND DISORDERS.

Hyperæsthesia, cutaneous, thermic, muscular, visceral. Paræsthesia, pressure on nerve. Anæsthesia, partial, drug. Analgesia. Hyperalgesia.

These are necessarily much less obvious to the veterinarian than to the physician of man. Yet in certain cases they may be observed directly, and in others deduced from dependent symptoms.

=Hyperæsthesia= is a state of exalted excitability of any part of the sensory nervous apparatus.

=Cutaneous hyperæsthesia= is that condition in which the slightest touch gives rise to an instant and extreme response. Some nervously organized mares which are dangerously ticklish and irritable, afford physiological examples. The surface soreness and sensitiveness which exist in the febrile chill, in wounds, dermatitis and neuralgia give pathological examples. It is further seen in certain cases of meningitis (cerebral and spinal), spinal irritations, rabies, tetanus and neuritis.

=Hyperæsthesia to cold= is seen in neuralgia, rheumatism, the early stages of many fevers (chill), in myelitis, neuritis, nerve injuries, and in posterior (superior) spinal sclerosis.

=Hyperæsthesia of the muscles= may be noted in tetanus, muscular rheumatism and neuralgia.

Visceral hyperæsthesia is shown in many cases of spasms of involuntary muscles (colic, arrest of intestinal calculi, gall stones or urinary concretions), and in inflammation of serous membranes (pleurisy, peritonitis).

=Paræsthesia.= This is a painful or morbid sensation caused by a lesion in the central nervous structures or in the nerves, but referred by the sufferer to some peripheral organ over which such centre presides. It may even be referred to an organ or part that has been amputated or otherwise removed. This may cause lameness of a kind to indicate suffering in a given muscle, tendon or joint, when the cause is purely central. In dourine, sexual acts are excited which have their real source in the nerve centres. The rabid dog snaps at imaginary flies in mid-winter, when such insects are only phantoms of his brain.

=Pressure on a nerve trunk= induces sensations of tingling, vibration, formication, heat, cold, and paresis, referred by the mind to the part to which that nerve is distributed, and when the pressure is removed these sensations recede in the order in which they came. This may explain some occult cases of lameness.

=Itching= may be a pure, persistent neurosis without any skin lesion. Treatment should then be addressed to the nervous system.

=Anæsthesia=, or absence of sensation, is in its degree partial or complete. The latter is familiar as occurring in parts the sensory nerves of which have been cut across, also in parts the sensory nerve or nerve centres of which have become completely degenerated. There is no response to the prick of a needle, the touch of a hot wire, to pinching or cutting. If the nerve remains intact as far as the spinal centres, reflex action may still occur, but the patient himself has no consciousness of this nor of the injury causing it. Accordingly, he makes no movement of head, ears, eyes, or other parts still dominated by the brain.

In =partial or imperfect anæsthesia= the response to irritation is less marked and may be even delayed. In some forms of central lesions the response to a prick may be delayed two, five, or ten seconds, or even more.

Anæsthesia causes awkwardness or uncertainty of movement, especially if the subject is blindfolded.

Anæsthesia may be =induced by medicine=, as in the general anæsthesia of etherisation, or the local anæsthesia caused by the topical application of cocaine or carbolic acid.

=Analgesia=, or insensibility to pain, may be present in cases in which ordinary sensations are still felt. It may be caused by cocaine, alcohol, and to some extent by carbolic acid.

=Hyperalgesia= is the opposite of this condition, and may be seen in certain irritable conditions of the nerve centres.

PSYCHIC SYMPTOMS AND DISORDERS.

Limitation in lower animals. Effects of age training, race heredity, individual and racial peculiarities, exhaustion, prostration, dementia, cerebral congestion, compression, degeneration, narcotics, ptomaines, toxins. Controlling absorption in another trouble. Delusions, hallucinations, vice, violence, œstrum, fatigue. Cerebral source of motions.

These have a much more restricted field in the lower animals than in man in keeping with the limitation of the mental faculties, and they may often be traced to demonstrated structural disorder. Yet some emotions of joy, fear or rage run very high and are comparatively unchecked by high mental development or mental training. The effect of training is, however, very marked in the more educated animals.

=Age= modifies by the sobering that comes from experience and habit. The frolics of puppies, kittens, lambs, foals and calves are in marked contrast with the sedateness and stolidity of old dogs, cats, sheep or cattle.

=Training= is seen in the educated horse which would have been panic stricken at sight of a locomotive, flag or floating paper, at the smell of a lion or bear, at the sound of a gun or drum, and which will now boldly face any one of these with no manifest tremor. The emotional puppy can be trained to soberly fetch and carry, to drive sheep or cattle without biting, to lie sentinel by his master’s property, to point at birds without seeking to catch them, or to carry shot birds without devouring them.

=Race heredity= comes from the training along the same lines in many successive generations. Thus the more domesticated breeds of dogs (shepherd, poodle, and greyhound) are very affectionate; other breeds (bull, mastiff, bloodhound) are lacking in this character. All trained races take naturally to the occupations of their ancestors. Some (horses, cattle and sheep) are easily panic-stricken, (stampeded). Some (turkeys, roosters) are not easily stampeded. Some (skunks), having effective sources, of defence, have little fear of man.

=Individual and racial mental dullness and torpor= must also be recognized. Some are stupid and slow, others alert and quickly responsive. Some horses are not level-headed and become uncontrollable in difficult situations. Some dogs are so emotional as to endanger their lives from sudden heart trouble. Some horses, dogs and cats will pine and die when separated from their fellows or human friends. Extreme timidity, or sudden rage may be so marked as to constitute a virtual morbid phenomenon. Sluggish cerebral and mental action may result from exhaustion, prostration, or dementia; also from cerebral congestion, pressure and degeneration; or from poisoning by narcotics, ptomaines or toxins (opium, hyoscyamus, Indian hemp, dourine, milk sickness, etc.). It may come from profound absorption in another object, as when the rabid dog bears whipping without a howl.

=Delusions= or =hallucinations= are shown in the rabid dog snapping at flies, or attacking his friend or master as an enemy, as well as in other forms of delirium. Narcotics, such as opium, Indian hemp, etc., ptomaines, toxins, and (in dogs) essential oils cause delirium by acting on the nerve centres.