In a case which came under my own observation, the blood of an anæmic girl was found, before the use of Iron, to contain only 50 parts of globules in 1000, instead of 120, the normal average. The Ammonio-citrate of Iron was prescribed, in five-grain doses, three times a day. After it had been continued for a month, the blood was again analyzed, and the amount of corpuscles found to have increased to 76 parts. After another month, they had reached to upwards of 100 in 1000 parts of blood. In the mean time the appearance of the patient had improved immensely. Chalybeates have thus a most immediate and obvious effect in restoring to the blood this wanting Hæmatosin. As the exact chemical condition of the Iron in Hæmatosin has not been discovered, so also the precise changes which Chalybeate medicines have to undergo before they can supply this deficient material in a fit and proper form, are not known. All the known soluble compounds of Iron, except the Ferrocyanide and Ferridcyanide of Potassium, possess this Restorative power. In most Chalybeates the Iron acts the part of a base; but in some, as the Ammonio-citrate and Potassio-tartrate, it exists in a peculiar condition, and cannot be precipitated from their solutions by Ammonia. The water of Chalybeate springs generally contains a Carbonate of Iron, held in solution by an excess of Carbonic acid. The same salt is contained in the compound Iron mixture and pill of the Pharmacop[oe]ia, when these are rightly prepared. When the Iron has entered the system, it is not necessarily excreted again from it, because it is not unnatural to the blood. To ascertain whether Iron given in small quantities is excreted by the kidneys, I have tested the urine of a patient who had been for some time taking thirty drops of the Tincture of the Sesquichloride twice a day: but I was unable to detect in it any trace of the metal. But when given in large doses, Iron passes off by the urine and by other secretions. Some portion may be excreted by the mucous membrane of the intestines, and combine in the cavity of the bowel with Sulphuretted Hydrogen. The resulting Sulphuret communicates to the fæces a characteristic black colour. The cause of this colour was ill understood; until pointed out by Berzelius. When the salts of Iron pass through the glands, they generally prove to be more or less astringent. The Chloride and Sulphate are most so; and they will thus be mentioned again under the head of Astringent medicines. The tincture of the Sesquichloride has obtained the reputation of being diuretic. But this constitutes no exception to the rule of its being astringent; for this diuretic power is owing to a peculiar ether, formed with the spirit by an excess of hydrochloric acid used in the preparation of the tincture.