The preparations used in veterinary medicine are white arsenic (arsenious acid), solution of arsenic, and the arseniates of iron and copper. This drug is a deadly poison, and should not be administered for any purpose save by the advice of a qualified veterinary surgeon, and in no case upon an empty stomach, as it is irritating to the mucous membrane of the alimentary canal. Notwithstanding this, carters and others are in the habit of giving large doses after fasting, for the expulsion of worms, and sometimes this has fatal consequences.
As an alterative, arsenic is given in small doses gradually increased. If given in a ball, the dose can be accurately apportioned and controlled, and combined with an alkaline solvent; but the practice of giving it as a powder is dangerous and objectionable, inasmuch as it is liable to fall to the bottom of the manger and to accumulate there, later to be taken as a fatal dose when that receptacle is licked clean after a bran mash or other moist food. The solution Liquor arsenicalis, or Fowler's solution, is the most satisfactory preparation, as it may be given in the food without incurring the risk referred to above. When arsenic has been administered for some considerable time, and it is desirable to discontinue its use, the dose should be gradually reduced and not suddenly discontinued, a remark that applies more or less to all alteratives.
Externally it is employed as a caustic in the form of a paste to destroy warts and other growths, and in weak solution as a parasiticide. Besides its alterative action when given internally, it is sometimes employed as a stomachic or stimulant to the stomach to aid digestion. It combines with the blood corpuscles, and the more readily when in combination with iron. All the organs and tissues of the body receive it from the blood, and for a time it remains incorporated with them; but it is eventually eliminated by the liver, the kidneys, and the skin, through the medium of their respective secretions, the bile, the urine, and the sweat.
Intractable skin diseases, especially those of a constitutional character, may often be treated successfully with arsenic given in the food. Where animals are known to suffer from periodical outbreaks of skin disease, a course of arsenic, especially if given during the moulting period, may have the effect of checking its eruption.