VOLATILE OILS 365 



are free from the impurities of artificial salicylic acid, while methyl 

 salicylate is of more certain composition than the oil. Both behave simi- 

 larly to salicylic acid therapeutically, although the oil is more of a local 

 irritant, and they are used for the same purposes as salicylic acid. 

 Either may be given in emulsion, or to dogs in capsules, and in combina- 

 tion with salicylic acid or salicylates. 



Methyl salicylate is serviceable in the following liniment for rheu- 

 matism : 



Tine. opii. 



Methyl salicylatis. 



Chloroformi aa oi- 



Lin. saponis ad. gviii. 



M. 



S. External use. 



The external application of methyl salicylate to acutely inflamed 

 rheumatic joints is one of the most efficient forms of treatment, and, 

 since some is absorbed, will take the place of the internal administration 

 of salicylates to a slight extent. It is usually best to combine this treat- 

 ment with internal medication, however. Plain gauze, or other absorbent 

 material, is saturated with methyl salicylate, applied to the affected j oint, 

 and then covered with oil silk, or rubber protective and bandage. 



SECTION IX.— VOLATILE OILS, OR DRUGS 

 CONTAINING THEM. 



General Action of Volatile Oils. 



Synonym. — Essential, ethereal, aromatic or distilled oils. 



Externally, volatile oils cause reddening of the skin (rubefacients), 

 sometimes blistering (vesicants), and often local anesthesia, notably oil 

 of cloves and peppermint. They are also parasiticide, antiseptic and 

 disinfectant, penetrating into the protoplasm o* bacteria. Internally, 

 these agents stimulate the flow of gastric, salivary and intestinal secre- * 

 tions and increase the vascularity and movements of the stomach and 

 bowels, and are antiseptic, stomachic and carminative. They therefore 

 temporarily improve digestion, overcome flatulence and colicky pain by 

 expelling gas from the stomach and intestines, prevent griping produced 

 by cathartics, and disguise and offset disagreeable effects and tastes of 

 medicines. In the digestive tract, volatile oils excite reflexly the nervous 

 system and heart, and augment the pulse rate and vascular tension. In 

 large doses, volatile oils are gastro-intestinal irritants. They often cause 

 polynuclear leukocytosis when ingested, but not when given intravenously. 

 The action is not specific but may be produced by agents irritating the 

 mucous membrane of the digestive tract. Volatile oils may be absorbed 

 from the skin, bronchial mucous membrane, and stomach. They are 

 eliminated by the skin, bronchial mucous membrane and kidneys, and ^ct 

 as antiseptics and parasiticides in the kidneys and lungs. 



In the process of excretion the parts are stimulated; vascularity, 



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