This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
Capsules, either hard or soft, are made of gelatin molded over a suitable object. Hard capsules, made in different sizes, have long been used for administering liquids as well as solids, while soft capsules, containing an admixture of glycerol to the gelatin, are used extensively for oils and oleoresins or solutions of active drugs in oils.
 
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