500)7680(15⅗ m. to 1 pint of solution (water). 500 ———— 2680 2500 ———— 1800 1500 ———— 300, or ⅗ of a m. N.B.—Divide the number of m. in 1 pint by the strength of the solution, and then divide the result by the percentage of original strength of the article. When original strength of solution is less than 100 per cent., as, for example, formaldehyd, which is 40 per cent., divide the quotient above resulting by the percentage of strength—viz.: 40)1536(38⅖ m. to 1 pint of solution (water). 120 ——— 336 320 ——— ¹⁶/₄₀ = ⅖. To get a ¹/₁₀₀ of a grain dose of any drug out of a solution of 60 minims containing ¹/₃₂ of a grain of that drug, compute as follows: ³²/₃₂ or 1 grain = 32 × 60, or 1920 m. ¹/₁₀₀ = ¹/₁₀₀ of 1920 m. 100)1920(19⅕ m. 100 ——— 920 900 ——— 20, or ⅕ m. RULE.—Multiply the quantity of the solution on hand in minims by a number indicating the fractional amount of the drug therein contained, and divide by a number indicating the fractional amount of the drug desired. In 20 parts of solution we have 1 part of carbolic acid. In 1 part “ “ ¹/₂₀ “ “ In 100 parts “ “ 100 × ¹/₂₀ = 5 pt. “ So that ¹/₂₀ solution is a 5 per cent. carbolic acid solution. 40 parts contain 1 part of carbolic acid. 1 part contains ¹/₄₀ “ “ 100 parts contain 100 × ¹/₄₀ = 2½ parts of carbolic acid. So that ¹/₄₀ solution is a 2½ per cent. carbolic acid solution. ACTION, USES, AND DOSES OF THE MOST IMPORTANT DRUGS. =Acetanilid.=—This substance, a derivative of anilin, is used to lower temperature; to relieve headaches and neuralgic pains; and to allay spasm, as in chorea and whooping-cough. Toxic doses cause lividity, cold sweats, ringing in the ears, and heart failure. The _dose_ is from 5 to 10 grains (0.3-0.6 gm.). =Arsenic.=—Arsenic is used internally as a tonic in anemia, an alterative in chronic constitutional diseases, as a special remedy in chorea, and as an anti-malarial. Externally, it is occasionally used as a caustic. The indications of its too free use are puffiness under the eyes, or griping pains in the abdomen, with diarrhea. Toxic doses cause abdominal pain, vomiting, purging, swelling of the face, and collapse.