INHALATIONS 721 



expressed juices, or of decoctions, infusions, or tinctures. 

 Selection is made of the solvent water, alcohol, or ether 

 which most readily removes the active principles. Where 

 two active principles, soluble in different media, are to be 

 dissolved out, the drug is acted upon by the two solvents 

 in succession, and the solutions mixed and evaporated. It 

 is important that evaporation be effected at low tempera- 

 tures ; heat above 150 Fahr. is apt to injure or decompose 

 many active principles. Well-made extracts keep for a 

 considerable time without change, especially in a cool, 

 dry place, and if occasionally moistened with rectified 

 spirit ; but when twelve months old they should be regarded 

 with suspicion. Of the B.P. extracts, veterinarians chiefly 

 use those of belladonna, hemlock, ergot, and Indian hemp. 



The liquid extracts are prepared from infusions, decoc- 

 tions, or weak tinctures, in the same manner as the semi* 

 solid extracts. Most liquid extracts are of such a strength 

 that one fluid ounce represents an ounce of the drug em- 

 ployed. Those chiefly used in veterinary practice are liquid 

 extract of cinchona, ergot, male fern, and opium. 



Green extracts, as Extracta belladonnas viride and hyos- 

 cyami viride, are prepared from fresh plants, the leaves and 

 tender stems being generally preferred. They are bruised, 

 the juice expressed, and gently heated to about 130 Fahr. 

 The green colouring matter is separated by filtration, the 

 strained juice is heated to 200 Fahr. to coagulate albumin, 

 again filtered, and the filtrate evaporated in a water bath 

 to the consistence of a thin syrup. The green colouring 

 matter previously separated is then added, and evaporation 

 continued, until a suitable consistence is attained. 



Abstracts are concentrated extracts, about twice the 

 strength of the corresponding fluid extract, and occur in 

 dry powder mixed with milk sugar. Many of these figure 

 in the U.S.P., including those of aconite, belladonna, hem- 

 lock, and digitalis. 



INHALATIONS-FUMIGATIONS 



Inhalations or vapours are volatilised applications in- 

 tended to soothe, stimulate, deodorise, or disinfect the nasal 



2z 



