ACTION AND USES.--Gentian is a pure bitter, and is prescribed as a stomachic and tonic for all classes of animals. Gentian improves the appetite and general tone. In atonic indigestion it is particularly useful amongst young animals, and in such cases is often conjoined with ginger and sodium bicarbonate. In relaxed and irritable states of the bowels and where intestinal worms are suspected, after administration of a laxative, gentian and dilute hydrochloric acid are of service. For horses suffering from simple catarrh few combinations are more effectual than an ounce of powdered gentian, two drachms potassium nitrate with two ounces of magnesium sulphate, dissolved in a pint of linseed tea, repeated morning and night. Where more general tonic effects are sought, iron sulphate is alternated with the gentian and salines. Gentian proves an excellent stomachic and stimulating tonic in influenza and other epizootics, helps convalescence from exhausting disorders and is a useful restorative for horses, overworked or suffering from loss of appetite or slight cold. The powdered gentian should be added to aloes when given in full cathartic doses to horses. HYDRARGYRI CHLORIDUM CORROSIVUM--CORROSIVE MERCURIC CHLORIDE--BICHLORIDE OF MERCURY--CORROSIVE SUBLIMATE ORIGIN.--Bichloride of mercury is obtained as a sulphate by heating a mixture of mercuric sulphate, sodium chloride and a little black oxide of manganese. PROPERTIES.--Heavy, colorless masses; soluble one in sixteen of water, one in three of alcohol; hydrochloric acid or muriate of ammonia increases its solubility. ACTIONS.--It is a corrosive, irritant poison; it is occasionally prescribed as an alterative, antiseptic and hepatic stimulant; repeated doses or long continued produce mercurialism. Externally, it is used as an antiseptic, astringent, caustic and parasiticide. It is a most powerful antiseptic when five parts of tartaric acid are added to one part of bichloride of mercury, which prevents the formation of insoluble albuminates of mercury in the tissues which checks any further action of the drug. Hydrochloric acid equal parts serves the same purpose.