338 IRRITANTS AND COUNTERIRRITANTS 



The following are representative prescriptions for cantharides 

 blisters : 



5 Cantharides. 



Cera3 Flavse aa S ij 



Adipis 5 xiv 



M. For external use. 



A stronger one is, 



IJ Cantharides. 



Euphorbii aa 2. 



Hydr. Chi. Corros 1. 



Petrolati 8. 



Cerati 12. 



or for deep action : 



^ Cantharides ^ J 



Hydrargyri lodidi Eubri aa 3 j 



Adipis S i 



Cautions in the Application of Counterirritants. 



1. Cantharides is not a safe blister for dogs, because it is liable 

 to cause too severe action. Furthermore, it may be absorbed from 

 the skin or licked off by the animal in sufficient quantity to produce 

 toxic action. 



2. Cantharides is contraindicated as a blister in urinary affec- 

 tions or cases of general debility or weakness. 



3. Counterirritants should not be used in acute inflammatory 

 conditions. 



SINAPIS ALBA (White mustard) and SINIPIS NIGRA (Black 



mustard). 



The former is the seed of Sinipis alba, and the latter the seed of 

 Brassica nigra. Both varieties are quite widely distributed in 

 Europe and America, often growing as weeds, but frequently culti- 

 vated. The mustard of commerce is usually a combination of both 

 varieties. 



Dose, Carminative. H. 3ij — iv; 8 — 16. 



Dose, Emetic. D. 3j — ij ; 4. — 8. In a ciip of warm water. 



Constituents. White mustard contains myrosin, a ferment, 

 and sinalbin, a glucoside. In the presence of water the ferment acts 

 upon the glucoside and separates from it an acrid fixed oil, Acrinyl- 

 iaothiocyanate. The black variety also contains the above ferment, 

 together with sinigrin, which in the presence of water yields a very 

 irritable, volatile oil (Oleum Sinapis Volatile — allyl-isothio- 

 eyanate). It is far too irritant to be used alone but may be used as 



