MEDICINAL BODIES ATTO PRINCIPLES CONTAINED IN DRUGS 71 



Oleum, pi. Oha. — Fixed oils are combinations of glycerin 

 ■with fatty acids ; usually oleic, stearic, margaric or palmitic 

 acids. They are liquid at ordinary temperatures and soluble 

 in benzin, chloroform and ether. Exposed to the air they 

 undergo acid fermentation, resulting in "rancidity." Fixed 

 oils are expressed from fruits and seeds of plants and animal 

 tissue. They are "fixed" because they cannot be distilled. 

 They leave a greasy mark on paper. 



Examples : Cod liver oil, castor oil, olive oil, linseed oil 

 and croton oil. 



Oleum, pi. Olea. — Fats are solid, fixed oils. 



Examples : Lard, cacao butter. 



Oleum destiUatum, pi. Olea destillata. — Distilled oils are 

 obtained by the distillation of flowers, fruits, leaves or seeds 

 of plants; by maceration, infusion, expression; or by 

 extraction with solvents. They are either liquid or solid 

 and possess an aromatic odor and taste. They are lighter 

 than water, and soluble in alcohol, ether, and very slightly 

 soluble ip water. Distilled oils are miscible with fatty sub- 

 stances and mineral oils. They do not leave a greasy mark 

 on paper. 



Synonyms : Essential oils, volatile oils and ethereal 

 oils. Alcoholic solutions of these oils are known as essences. 



Examples : Gil of peppermint, oil of cloves, oil of win- 

 tergreen. 



Oleo-resina, pi. Oleo-resince. — Oleo-resins are semi-solid 

 mixtures of resins and volatile oils. Many are natural 

 products, exuding from trees, as crude turpentine, which 

 contains the volatile oil of turpentine and a resin, or what 

 is commonly termed " rosin." They are soluble in ether. 



Examples : Oleo-resin of capsicum, oleo-resin of aspi- 

 dium.. 



Eesina, pi. Besince. — Eesins are brittle, amorphous solids, 

 soluble in alcohol and alkalies. They are obtained from 

 oleo-resins by simple distillation, as in the case of turpen- 

 tine ; or may be extracted from plants by means of heat or 

 alcohol. 



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