C A NTH A R IS. 383 



which are two membranous transparent wings ; odour strong 

 and disagreeable. Powder greyish-brown, containing shining 

 green particles. 



Substance resembling powdered Cantharis : Kamala, which 

 has no shining particles 



Composition. Cantharides contains '20 to -50 per cent, of 

 cantharidin^ a greenish volatile oil, and peculiar fatty bodies. 

 Cantharidin, Ci H 12 04, is obtained as shining colourless 

 prisms, soluble in ether, chloroform, alcohol, and oils, and is 

 the active principle, being a most powerful irritant. Some of 

 the other properties of cantharides may possibly be referable 

 to the oil. 



Preparations. 



1. Acetum Cantharidis. 1 in 10 of Glacial Acetic, and 



Acetic Acids. 



2. Charta Epispa.stica. 



3. Emplastrum Cantharidis. 1 in 3. 

 1. Emplastrum Calefaciens. 1 in 24. 



5. Liquor Epispasticua. Cantharides. 8; Acetic Acid, 4; 



Ether, to 20. 



6. Tinctura Cantharidig. 1 in 80. Dose, 5 to 20 min. 



7. Unffuentum Cantharidis. 1 in 7. 



ACTION AND USES. 

 1. IMMEDIATE LOCAL ACTION AND USES. 



Externally. Cantharis is a rubefacient and vesicant when 

 applied to the skin, acting upon the nerves and vessels of the 

 part like mustard and other measures of the same class, as de- 

 scribed under Sinapis, to which the student is referred. Its 

 effects differ from those of mustard chiefly in being much less 

 rapid, but of a more severe degree. The Emplastrum or Charta 

 has to be applied for a few hours before a sense of smarting, 

 heat, and burning, is felt in the part ; small vesicles then form, 

 and at the end of eight to twelve hours have united into a 

 single largo bulla. The removal of the plaster after six 

 hours, and the application of a poultice, will " raise the blister " 

 more effectually and pleasantly. Vesication is decidedly more 

 rapid after the application of the Acetum or Liquor Epispasticus. 

 When the blister has been developed, the fluid is carefully 

 incised, and the raw surface encouraged either to heal by 

 simple dressing, or to discharge by the application of 

 irritant ointments, such as Unguentum Sabinae. Cantharis is 

 the vesicant in ordinary use for purposes of counter-irritation. 



