An obsolete system of fluid measure used by unfortunate pharmacists of an earlier, quainter time. Like the Apothecaries' weight, it has widely been supplanted by metric units of measure; even in the United States, which tends to be rather reactionary in these matters. The units:

60 minims = 1 fluid dram
8 fluid drams = 1 fluid ounce
16 fluid ounces = 1 pint
2 pints = 1 quart
4 quarts = 1 gallon

Apothecaries' fluid measure is, however, somewhat less confusing than Apothecaries' weight, since the larger units (pint, quart, etc.) are equivalent to those used in the "standard" English system.