302 OBSERVATIONS ON BLISTERING PLASTER. 
ART. LVIII.-OBSERVATIONS ON BLISTERING PLASTER. 
By William Procter, jr. 
The importance of having this preparation of such decided 
activity, that it can be depended upon, particularly in extreme 
cases, can readily be appreciated by medical men. That the 
continuance of life sometimes hangs on the efficiency of this 
agent, will be hardly disputed, and any addition to its power 
should certainly claim the consideration of the physician, 
who has the interest of his patient at heart; and of the 
pharmaceutist who is jealous of his good reputation. 
Having occasionally had blistering plasters to fail in pro- 
ducing vesication, notwithstanding the cantharides which 
entered into their composition were of good quality; and 
having experienced the mortification of hearing a report of 
their failure from the patient or his physician, the writer, 
after some experiments on this subject is led to believe that 
blistering plaster, made from good flies, often fails in producing 
its peculiar effects, owing to the manner in which the prepara- 
tion is made and applied. 
The first point to be attained, is, in all cases, the possession 
of Cantharides of known excellence, very finely divided. 
The next is presenting them in a vehicle which will readily 
hold their active principle in solution, and which, when 
applied to a surface, will be active at every part in contact 
with it; at the same time that it will retain consistence 
enough to prevent it from spreading when heated by the 
skin. 
And lastly, it is of great importance that the material em- 
ployed on which to spread the plaster, be of such a character 
as not to absorb the fluid part of the cerate, and thus deprive 
it of its adhesive power as well as much of its activity. 
An error which has been generally countenanced by writers 
on this subject, is that flies are liable to be injured by the heat 
