Part 34

Pains due to pressure on the nerves by tumors, aneurisms, and other swellings, are constant, whereas neuralgic pains are marked by remissions and aggravations and even by intervals of complete relief.

Causes. The toxic neuralgias are illustrated by chronic lead poisoning, in which, in man, there are wandering pains like those of rheumatism, and in the lower animals muscular stiffness and contractions which suggest a similar condition. In man, too, gout is a common factor, and in pigs and birds in which this condition exists, stiffness and evidence of suffering may well be at times attributed to a similar cause. How many other forms of chronic metallic poisoning and poisoning by morbid autochthonous products of indigestion are attended by disorders of innervation and nutrition, it is as yet impossible to say. The direct action of cold, an anæmic condition of the nerves, and reflex action from distant sources of irritation are among the other invoked causes. Inflammation in the nervi nervorum is also invoked as a factor, but in this case the symptoms would not accord with the rule given above, since the nerve trunks would be very tender to touch or pressure, and the suffering would be unshifting and shown permanently in the one seat.

=Facial Neuralgia.= Lafosse and Zundel describe as cases of this kind those in which periodically the horse’s eyes are fixed and shining, the ears drawn back and depressed as in vice, the head at intervals bent on the neck, with plaintive neighing, rubbing the head on the stall and pawing. Those cases of twitching of the head or rapid jerking of the ears in horses, when they have been driven for some distance, and which are relieved by wearing a close net over the nostril or by section of the trifacial nerve at the infra-orbital foramen, manifestly partake of this character.

=Cervico-Occipital Neuralgia.= Lafosse speaks of this as often mistaken for torticolis, the head being turned to the affected side during the paroxysms. In man this is often a result of cold draughts on the back of the head, and associated with tender points on the course of the nerve, between the mastoid and the median line.

=Dorso-intercostal neuralgia= causes pain in deep inspiration, and =lumbo-abdominal neuralgia= develops tenderness in the loins, in one testicle, or in one lip of the vulva according to Lafosse. Diagnosis between such cases and neuritis, spinal disease, and other obscure nervous affections must be very problematical.

=Sciatic Neuralgia.= This is described by Zundel as causing jerking and lameness in the affected limb, sometimes aggravated and sometimes improved by work and associated with muscular weakness or paresis. Sciatica in man is, however, rarely a simple neuralgia, but partakes rather of the nature of a neuritis, and there is no good reason for supposing that the disease of this nerve in the lower animals is other than an inflammatory condition.

Leclainche after consideration of the testimony adduced, is of the opinion that we still lack absolute evidence of uncomplicated neuralgia in the domestic animals.

Treatment. For =toxic= cases elimination of the poison is the first consideration. For lead carefully graduated doses of iodide of potassium to carry off the offending agent without increasing its poisonous action must be continued as long as the metal is passed by the urine. It may be followed by a course of strychnia, by electricity, massage and blisters. Gouty subjects may be treated with salicylate of soda, alkalies, or colchicum. The victims of Bright’s disease must be treated for the kidney affection.

Where there has been =trouble of the digestive organs=, intestinal antiseptics (salol, sodium salicylate, bismuth-salicylate, beta-naphthol) and small doses of arsenious acid will sometimes benefit.

In =anæmic conditions= a course of tonics (cod liver oil, iron, quinine, nux vomica) are indicated, and, to improve the local blood supply, nitro-glycerine. A rich stimulating ration, currying, an open air life, and sunshine (in summer a run at grass) are called for.

In man with a suspicion of =traumatic origin=, W. H. Thomson strongly advocates a persevering use of the hot water douche to the parts first affected, the hypodermic use of morphia and atropia, and in case of local anæmia nitro-glycerine every three hours. Where there is a suspicion of inflammation he successfully employs absolute rest, with opium narcotism so as to abolish the pain, for twenty days if necessary. Aconite, antipyrin, acetanilid, phenacetin, exaglin, and gelsemium have their advocates, and may benefit in individual cases. A course of arsenic is often successful, and phosphorus and ergot have each proved of value.

ATROPHY OF NERVES.

From arrest of function, from lesions, pressure, distal, but at times central of lesion. Symptoms: Loss of function advancing to paralysis. Muscle atrophy. Prognosis: in absence of incurable cause, is hopeful. Union of divided ends, restoration of function. Treatment: time, ligature of divided ends.

This is usually the result of arrest of function. It may be due to transverse section of the nerve, as in surgical neurectomy when the separated peripheral end of the nerve gradually wastes. It may come from contused wounds implicating the nerve and causing destruction of its substance. It may be from tumors or other neoplasms pressing on the trunk of the nerve and preventing the passage of nerve currents. Or, inflammatory effusion may press on the nerve, as happens often to the crural in hæmoglobinuria. Or the pressure may come from enlarged mediastinal glands, or even from the distended posterior aorta under habitual violent exertion so as to permanently incapacitate and atrophy the left recurrent laryngeal nerve as in chronic laryngeal paralysis (roaring). Similar wasting occurs in other nerves under corresponding conditions. Atrophy may, however, extend centrally from the peripheral end of a nerve when it can no longer remain functionally active. We find an example of this in the atrophy of the optic nerve up to the commissure when the eyeball has been excised. A similar condition is often seen in horses in which the integrity of the eye has been completely destroyed in connection with recurring ophthalmia.

The symptoms attendant on atrophy of a nerve are those of impaired function gradually advancing to complete paralysis of motion or sensation. In cases of a complete breach of continuity as in section or severe traumatism the entire loss of function necessarily precedes the atrophy. Again, when it comes from destructive changes in the coats and media of the eye, and of the ganglionic cells of the retina, the atrophy of the nerve trunk proceeds simultaneously with the lesions of the organ of vision.

The diagnosis will in many cases be easy as deduced from the traumatic or surgical lesion. In other cases it may be made with certainty from the complete muscular paralysis, wasting and degeneration of the muscles supplied by the nerve, and by the history of the case (hæmoglobinuria in atrophy of the triceps extensor cruris, roaring in atrophy of the laryngeal muscles and recurrent nerve). In other cases, as in the eye, we have the atrophy of the eyeball, the distortion or complete paralysis of the iris, the opacity of the lens, or the exudation into the vitreous, choroid and retina when these can still be observed.

Prognosis will depend on the cause. With a nerve severed with a knife or crushed in a part of its course and atrophied, without destructive changes in the organs in which it is distributed, repair is possible and to be expected in time.

Treatment is expectant, yet inflammation must be subdued, tumors removed, divided ends ligatured, etc.

DISEASES OF THE URINARY ORGANS.

Relative prevalence in man and animals. Causes of difference. Kidneys as eliminating organs for nitrogenous material, toxins, bacteria, mineral, vegetable and animal poisons, diuretic drinking water, condition powders, cantharides, urea, etc. Suppression of urine, precipitation of urine. Filtration through kidney. Secretion. Urinary solids. Nervous control of secretion. Excess.

Diseases of the urinary organs are less prevalent in the lower animals than in man, owing largely no doubt to the greater simplicity of their habits of life and to the comparative shortness of the lives of those that are kept for meat producing. It is a mistake, however, to suppose that they are so infrequent as would appear, since the absence of subjective symptoms in the animal allows a number of the milder forms of renal disease to be passed over without recognition.

In man the excessive consumption of animal food, the lack of exercise, the abuse of alcohol, the prevalence of venereal diseases, conduce largely to renal troubles, while animals in general escape. Yet animals suffer much more extensively than is generally supposed. The kidneys are, as in man, the eliminating organs for superfluous and waste nitrogenous matter, and in overfed animals may be overcharged with this work. They are the general emunctories for the soluble poisonous products of bacteria and plants, which may stimulate the urinary secretion, and from these irritation may result. It is through the kidneys that the bacteria themselves largely leave the animal body, and trouble is liable to come during their passage. Further, exposure to cold tends to =increase the urinary secretion=, over-stimulating the kidneys, and the same may come from diuretic drinking waters and condition powders, also from cantharides and other diuretic agents applied to the skin. Urea and many toxins are diuretic, hence the occurrence of polyuria at and after the crisis of fevers.

On the other hand =suppression of the urinary secretion= may occur in connection with profuse perspirations in hot weather, with prolonged diarrhœa, or with privation of water, and in such cases the liquid becomes concentrated and irritating and there is a disposition to precipitate its solids under slight disturbing causes. As conducive to such precipitation may be named foreign solid bodies, bacterial ferments and probably the goitre poison since gravel and calculus are common in goitrous regions.

There are two forms of elimination through the kidneys. 1, filtration; 2, secretion.

1. Filtration is referred to the glomeruli, and is determined by the relative blood pressure. Increase of pressure causes increase of watery transudation. Digitalis increases heart action and arterial pressure, and accidently urination. Excessive consumption of water and watery liquids increases intravascular tension, and the amount of urine.

2. Secretion is referred to the columnar epithelium of the convoluted tubes. It is by the elective affinity or selective power of this epithelium that the solids of the urine are abstracted from the blood and passed into the urine. Crystals of uric acid have been found in these cells and it is supposed that the abundance of water furnished by the glomeruli, irrigating these convoluted tubes, dissolves and washes on the various solids and other products with which the epithelial cells are charged. The protoplasm of the cells becomes saturated with the urea, uric acid, hippuric acid coloring matter (indican, urochrome, etc.), and this is washed out, passing by exosmosis to the liquid of lesser density with which the tubes are filled.

Nervous Control of Urinary Secretion.

An electric current through the renal plexus of the sympathetic (vaso-motor) lessens, or suppresses urinary secretion (inhibition).