When mixtures are to be administered in parts it will be found that bottles of best quality with moulded graduations are fairly reliable. It is easy to tell at a glance any that may be seriously inaccurate. In dispensing potent medicines, the accuracy of the bottom graduation should always be ascertained, and in all cases the top dose should be correctly measured in. Printed slip graduations may be grossly inaccurate unless used as follows : Measure one dose into the bottle, affix the slip so that the bottom dose-mark is level with the liquid; also measure in the top dose when finished. The nearest approach to perfection is in the use of a blank slip graduated by hand; affix the slip to the empty bottle, and, if of variable calibre, measure in and mark each dose. Bottles having sides of nearly uniform thickness may quickly be satisfactorily graduated thus : Affix the slip, measure in and mark one or two doses (using the prescribed vehicle for the purpose), dispense, and when filled up pour back one dose into the measure and mark the level of the liquid in the bottle ; finally divide the ungraduated space into equal divisions of the requisite number.