90 PKESCEIPTION WRITING 



and phrases understandingly. The directions to the 

 attendant are heralded by the Latin Signa, or Signetur, 

 meaning label, or let it be labelled ; abbreviated, " Sig.," or 

 merely " S.," and being for the use of the attendant of the 

 patient, are in English. The directions should be very 

 precise. One should not write : " Use as directed," or " Give 

 in water," but indicate exactly the quantity of medicine to 

 be administered, the precise amount of water with which it 

 is to be diluted, and the time at which it is to be given. 

 For instance : " Give one tablespoonful in half a pint of 

 water three times daily after feeding." 



Poisons should be marked as such. It is well some- 

 times to indicate that the prescription is " for a horse," in 

 order to avoid mistakes and to quell the qualms of the 

 conscientious druggist. 



Preparations which are not to be used internally should 

 be labelled " external use." Under " Signature " the name 

 of the. writer and date is included. If desirable, one may 

 inscribe " Do not repeat." Quantities used in prescription 

 writing are indicated by the signs of the apothecaries or 

 Troy system of weights for solids. For liquids, signs rep- 

 resenting units of the wine measure are employed. The 

 Troy grain and ounce are used by apothecaries as units of- 

 weights in dispensing prescriptions. In ordering large 

 quantities (as pounds) the avoirdupois pound of 16 ounces 

 is employed, and in buying ounces of drugs without a pre- 

 scription the avoirdupois ounce is also utilized. The 

 avoirdupois ounce contains 437 grains ; the Troy ounce 

 contains 480 grains. The grain is of similar value in both 

 systems. 



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