RPI. | 41s 
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ae SS 
EPISPASTICS. 
_ ‘External applications which inflame the skin, 
ppd cause an effusion of serum under the cuticle. 
This serous deposition is contained in large vesi- 
cles, which consist of the cuticle raised above the 
true skin, and separated from it by the contained 
fluid. It is liberated either by the spontaneous 
rupture of these vesications, or by puncture. The 
discharge from the inflamed and denuded surface 
then becomes, in 4 short time after, puriform. 
The common blistering fly produces, thus exter- 
nally applied to the cuticle, a train of effects 
which may be considered the type of the oper- 
ation of these agents. Every one knows that 
these effects are what in common parle is termed 
a blister. The immediate action of cantharides 
applied to the cuticle, is evidently by their stimu- 
lant influence on the cutaneous blood vessels, ex- 
citing them to increased energy and thus producing 
cutaneous inflammation. Serous effusion by the 
exhalent extremities of these vessels, is a natural 
consequence of this. In so far, the effect of a blis- 
ter is stimulating. The subsequent conversion of — 
the serous discharge toa puriform one, is the next 
natural effort of the diseased surface, to resolve 
itself, and restore healthy action. The puriform 
discharge continues a short or a longer time, ac- 
cording in some measure to the condition of the 
individual system, but chiefly in consequence of 
the nature of the dressings applied. If they be of 
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