y» MATERIA MEDICA. 



by the part to which it is to be applied. Sometimes a thin gauze is 

 interposed between the skin and cerate, which is thought to prevent 

 the absorption of the active principle. From six to eight hours is 

 sufficiently long to allow a blister to remain on : if vesication has 

 not then taken place, a warm poultice is to be applied. For children, 

 a much shorter time will suffice. The best dressing is simple 

 cerate ; or, if to be kept discharging, basilicon ointment ; if not dis- 

 posed to heal, a mixture of Goulard's and simple cerate. The 

 strangury, often resulting from the application of blisters is best re- 

 lieved by an anodyne enema, and the free use of diluents. 



TJngue?itum Cantharidis, (U. S.) — Used only for dressing blis- 

 ters, to maintain the discharge. 



Emplasto-um Ficis cum Cantharide, (U. S.) — Emplastrum, 

 calefaciens, or warming jylasier . Prepared by melting together the 

 cerat. cantharidis with Burgundy pitch. Used as a gentle rubefa- 

 cient in chronic cases. It sometimes causes vesication, particu- 

 larly if improperly made. 



Linimenium Cantharidis^ (U. S.) — Made by digesting cantha- 

 rides in oil of turpentine. A very powerful, prompt, and stimulating 

 liniment, and vesicant. Used sometimes in typhus fever. 



Other species of the Cantharis possess vesicant properties, par- 

 ticularly the C. vittata or potato-fly^ which is indigenous. It is 

 smaller than the preceding, but resembles it in all its medicinal 

 properties, 



CLASS XVI. --RUBEFACIENTS. 



" Medicines which cause inflammation of the skin, when applied 

 externally." The indications- for their use, as well as the principles 

 of their operation, are very much the same as those of epispastics. 

 The latter are preferred when a slow and stimulant effect is desired ; 

 the former, where the impression is to be sudden and transient. 

 Rubefacients cannot deplete like blisters ; they are likewise inferior 

 in their power of breaking up morbid associations, as in intermittents. 

 As revulsives, rubefacients are most useful in spasms and nervous 

 irritations ; blisters, in local inflammations. 



Burgundy Pitch. — (Pix Abietis, U. S.) 



Product of the Abies communis or Norivay spruce fir^ a lofty 

 evergreen, native of northern Europe. Procured by stripping off" the 

 bark, under which it concretes in large masses; then melting in 

 boiling water, and straining. A spurious pitch is manufactured out 

 of rosin and common pitch. — It is hard, brittle, and of a yellowish 

 brown colour, of a weak terebinthinate odour and taste ; usually con- 

 tains many impurities. Used in the form of plaster to the skin, 

 where it produces a mild rubefacient effect. In some persons it 



