These are liquid or solid substances, unctuous to the touch and characterized by inflammability. They are divided into two classes, the fixed and the volatile, because distinguished, as their names imply, most readily by their different behavior on the application of heat.
(Don't ask me why oils are found under "Oil of ...", "Olea", and "Oleum ...". This sort of disorganization is the norm for this particular dispensatory. - Henriette)