Vitriol (sulphate of iron and sulphate of copper) was the iron medicine most in use up to the sixteenth century; but it was not given with the special intention of giving iron. Paracelsus had great faith in the Arcanum Vitrioli, which, indeed, appears to have been sulphur. He also introduced the use of the magnet, but only externally. It was in the century after him that the salts of Mars came into general medical use. In the course of the seventeenth and eighteenth centuries the preparations of iron became very numerous. Iron filings brought into an alcohol, that is very finely powdered, were much employed, sometimes alone and sometimes saccharated, or combined with sugar candy. Crocus martis was the sesquioxide, æthiops martial was the black oxide, and flores martis, made by subliming iron filings and sal ammoniac, yielding an ammoniated chloride of iron, was included in the several British pharmacopœias of the eighteenth century.
The association of iron with Mars probably influenced the early chemical physicians in their adoption of iron salts in anæmic complaints, and as general tonics. The undoubted effect of iron remedies in chlorotic disease was naturally observed, and the reputation of the metal was established for the treatment of this condition long before it was discovered that iron is an invariable constituent of the human body. When this physiological fact came to be recognised it was supposed that the action of iron salts was explained; but, in fact, the investigations of the last century have only tended to make this theory doubtful.
It is known that in health the proportion of iron in the body is fairly constant. An average man's blood contains about 38 grains, almost all of which is con-
