This drug is employed in agricultural operations of various kinds, and is a frequent cause of poisoning in horses and other animals. Ignorant carters and grooms persist in using it to destroy worms and produce a glossy coat, with little regard to its dangerous properties. Teamsters often give it with antimony, and without causing any mischief at the time. Arsenic, however, is one of the cumulative poisons, and ill consequences may follow long after its habitual use has been discontinued.
Cases of wilful poisoning by the drug are found recorded in veterinary literature, but many occur also from the careless employment of sheep-dipping compounds and "weed -killers", which in various ways gain entrance to the food and drink of animals.
These preparations, composed of arsenic, with caustic alkalies to facilitate their solution, have a saline taste attractive to horses, and particularly to cattle, which will lick an open packet of arsenical powder with evident relish, and no season passes without deaths resulting from such compounds being left within their reach. Weed-killer is poured upon garden-paths and carriage-drives, and animals have been known to succumb after eating the weeds before wet weather has washed it into the soil. Refuse paints, containing emerald green, Scheele's green, Brunswick green, where cast upon pasture land in manure, are sometimes followed by fatal results. The death of some valuable horses was caused in one instance by a tin of this fluid being upset and becoming mixed with the corn. Arsenic is used also as a dressing for wheat, and a poison for vermin, and less frequently as a cure for warts and foot-rot.
Although there is much difference in the susceptibility of animals, as proved by the experiments of Hertwig, Percival, Gerlach, and others, the action of this poison is largely governed by the condition of the stomach as to the presence or absence of food. The quantity of food in the stomach has also a great influence in delaying the toxic effects of the drug. In one of Percival's experiments upon a glandered horse an increasing daily dose was given with food until, on the seventeenth day, it had reached 380 grains, making a total of 7 ounces in all. Even this large quantity failed to produce any physiological effects. On the other hand, the fatal effects of much smaller quantities were seen in the case of eleven cart-horses which were poisoned at Edgware by drinking out of a bucket that had previously been used for sheep-dip, one of the animals dying in ten minutes, and several more within the hour. The quantity taken by each horse in this case must have been small, but there is reason to think that the empty condition of the stomachs had rendered them more susceptible of its action.
Poisoning by arsenic is sometimes very sudden, and at others slow and progressive; the one being spoken of as acute poisoning, the other as chronic or cumulative. In the chronic there may be an appearance at first of improved tone, shiny coat, strong pulse, and good spirits; these being maintained by what would be called the "arsenic habit" but for the fact that it is involuntary on the part of the animal. After using it for a time it fails of effect, and the carter is tempted to increase the dose, until presently appetite fails and is ultimately lost, the coat stares, shivering-fits follow, colicky pains set in, and are succeeded by purging, prostration, imperceptible pulse, staggering, falling, and death. In the acute form of the disease there is sudden and desperate illness without premonitory signs, those even who are quite unaccustomed to animals recognizing the rapid approach of death by the haggard countenance, quick breathing, and violent trembling of the body, and general distress. The skin is bathed in sweat, the ears and legs are very cold, the eyes are protruding and bloodshot; tears run down the face, the lining membrane of the nostrils is intensely red, and a watery fluid or vomited matter flows from them. In some instances the lips may be greatly swollen, the gums inflamed, and the tongue so enlarged as to be contained in the mouth with difficulty; frothy saliva of a ropy consistence and offensive odour hangs from the lips. The patient will frequently throw himself down in his agony, but towards the end he will endeavour to stand, and when no longer able to keep his feet he falls and dies with a few painful struggles.
In the chronic or accumulative form of arsenical poisoning not much can be hoped of antidotes, as the drug is already absorbed or out of the reach of chemical agents which might counteract it. Attention should therefore be directed to minimizing its effects and sustaining the patient with suitable nourishment until the poison is eliminated from the system. Milk and eggs, gruel, linseed, barley-water, and alcoholic stimulants may all be employed to support the animal until the vis medicatrix natures can assert itself. Iron in combination with nux vomica, given in small repeated doses, will aid in bringing about this much-desired result. In the acute form of the disease a dose of the peroxide of iron should be promptly administered. This agent is most effectual when precipitated from a solution of persulphate of iron by the addition of ammonia, and afterwards washed with warm water and given at frequent intervals until enough has been taken to neutralize the poison. The proportion of peroxide of iron required to produce this effect is estimated by Mr. Finlay Dun to be twelve times the amount of the arsenic taken.
Epsom salts in solution, mixed with liquid caustic potash (liquor potassae), produce a gelatinous hydrate of magnesia, which greatly retards the solubility of arsenic, and may therefore be given with advantage. The yolk of eggs, linseed and other fixed oils, charcoal, clay, and starch all help to hinder mechanically the effects of arsenic upon the walls of the stomach and intestine. Long and careful nursing is needed, and the temperate use of diuretics is calculated to assist nature in getting rid of the poison by the natural channel of the kidneys.