CANTHARIDES * 613 



transparent, brownish wings, elsewhere of a shining, coppery- 

 green color. The powder is grayish-brown, and contains 

 green shining particles. Odor strong, and disagreeable; 

 taste slight, afterwards acrid. 



Constituents. — 1, the active principle is cantharidin, 

 C10H12O4 (2 per cent.), in colorless scales, insoluble in water, 

 soluble in alcohol, ether, chloroform, oils, acetic acid and 

 acetic ether ; it is found chiefly in the generative organs, 

 eggs, and blood of the beetles ; 2, a volatile oil ; 3, a bland, 

 green oil ; 4, acetic and uric acids, extractives and salts ; 

 cantharides deteriorates with age and should be kept 

 unpowdered in tightly stoppered bottles. 



Dose.—R. & C, gr.v.-xx. (.3-1.3); Sh. & Sw., gr.iv.^viii. 

 (.24..5) ; D., gr.i.-ii. (.06-.12). 



PREPARATION. 



Tinctura Cantharidis, Tincture of Cantharides. (U. S. P.) 

 Made by percolation of cantharides, 50; with alcohol to ma£:e 

 1000. (U. S. P.) 



Dose.— H.&C, 3ii.-iv. (8.-15.); D., mii.-xv. (.12-1.). 



Action External. — Cantharides, by virtue of cantharidin, 

 is an intense irritant. When applied to the skin in ointment 

 it produces no effect for several hours, but after that time 

 causes dilatation of the cutaneous vessels, hypersemia, and 

 blisters, which appear in from 3 to 12 hours. The blisters 

 soon break, discharge their serous contents, and then dry 

 and crust the surface. If the action of cantharides is main- 

 tained continuously; if the application is repeated, or 

 covered with a bandage; or -if the skin was previously 

 inflamed, then inflammation of the deeper-seated parts 

 ensues, followed by suppuration, sloughing, loss of tissue, 

 destruction of hair follicles, and scars. The drug is thera- 

 peutically a rubefacient and vesicant, and counter-irritant, 

 in occasioning dilatation of the superficial vessels, and 

 reflexly, contraction of those in the remote underlying parts. 

 Cantharides acts more powerfully on the skin of horses and 

 dogs, than on that of cattle and swine. If applied over an 

 extensive surface, absorption and poisoning may occur. 



