Iron in its various forms, but more particularly in certain solutions, has a direct effect upon the tissues with which it comes in contact and before it enters the circulation.

It is more or less strongly astringent in proportion to the strength of the solution, and may be made to exert its influence on various external and internal parts, as the mouth, throat, gullet, stomach, and bowels. Blood and other albuminous fluids are coagulated by the salts of iron, and this property is made use of in medicine to arrest haemorrhage or bleeding both from internal organs and external parts. Its constringing effect leads to its employment in obstinate cases of diarrhoea and catarrhal conditions, of mucous membranes generally.

By the administration of iron the faeces are blackened as a result of the formation of sulphide of iron in the intestinal canal. With the horse we have seldom those irritable conditions of the stomach which in the human subject preclude the use of iron. Any existing difficulty in this direction may be overcome by selecting the least irritating preparations, as the saccharated carbonate and reduced iron.

The chief value of iron is due to its action upon the red corpuscles, and through them upon the organs and tissues of the body. It is therefore prescribed in cases of wasting and mal-nutrition, and in haemorrhage to arrest the flow of blood, as well as in the case of chronic discharges from mucous membranes. It is also given in purpura and similar blood disorders.

In combination with other agents, as strychnine and arsenic, quinine and vegetable bitters, iron is given as a nerve-tonic and muscle-builder. With iodine it is prescribed for the removal of effusions, as those in the chest cavity resulting from pleurisy, and for the reduction of glandular swellings and bony deposits on the limbs and other parts of the body. As an astringent application it is sometimes used for grease and applied to indolent sores and ulcers.

As an antidote in cases of arsenical poisoning, iron is used in the form of hydrated oxide.