As to olive oil, we have abundantly treated of its nature and elements already.2998 It now remains to speak of the medicinal properties of the various kinds of oil. The most useful of all is omphacium,2999 and next to that, green oil;3000 in addition to which, we may remark that oil ought to be as fresh as possible, except in cases where old oil is absolutely required. For medicinal purposes, too, oil should be extremely fluid, have an agreeable smell, and be free from3001 all taste, just the converse, in fact, of the property which we look for in food. Omphacium is good for the gums, and if kept from time to time in the mouth, there is nothing better as a preservative of the whiteness of the teeth. It checks profuse perspirations.