timeter ; the centigram is not needed. By writing Gm. for gram all fear of its being mistaken for gr. or grs. is removed. Use the decimal line instead of points. It makes error impossible, and gives shape to a prescription. A metrical prescription with the line will look similar to the following : -Gm. R7 Hydrarg. bichlor.|10 Potassii iodidi.31 Tr. cinchón, comp.125