THE VOLATILITY AND SOLUBILITY OF CANTHARIDIN. 51 
not to evaporate all the water, as on the existence of the 
aqueous extract in a soft state depends much of the efficiency 
of the preparation as an irritant dressing. 
(i d. In the Linimentum Cantharidis, U. S. Pharm., in which 
an ounce of flies is digested in eight fluid ounces of oil of 
turpentine, the cantharidin is to the menstruum as 1 to 1500 , 
a proportion probably quite sufficient to retain it in solution. 
The importance of the officinal direction to digest is evident. 
It is quite doubtful whether this liniment, as made by the 
process of Dr. Jos. Hartshorne, one part of flies to three 
parts of oil, will retain all the cantharidin after standing 
awhile. 
“ e . The Acetum Cantharidis, (Lond. Ph.) made by macera- 
ting an ounce of flies in ten fluid ounces of acetic acid, 1 * 48 , 
has been criticised by Mr. Redwood, ( Pharm . Journal , Oct. 
1841 ,) who arrived at the conclusion that it owed its vesi- 
cating power almost solely to the acid, he not being able to 
discover cantharidin in it. The inefficiency of cold acetic acid 
as a solvent for pure cantharidin has been proved by the 
above experiments, and its efficiency when hot equally 
shown. There can be but little doubt that the London 
preparation would be much improved by digesting the flies in 
the acid for an hour in a close glass vessel at the temperature 
of boiling water. 
“ f The cantharidal collodion of M. Ilisch has been con- 
siderably used as a vesicant in this country. Ether being a 
good solvent for cantharidin readily keeps that principle in 
solution. When applied to the skin, the escape of the ether 
leaves a coating of ethereal extract of cantharides, admixed 
with collodion. This preparation sometimes fails from a 
deficiency of cantharidin, at other times from want of a 
sufficient body in the collodion excipient, and it has been 
found more advantageous to treat the cantharides with ether 
till exhausted, distil off the ether, and add the oily residue to 
collodion of the proper consistence. The addition of a little 
olive oil, and of Venice turpentine, as recommended by Mr. 
Rand, will give more activity to the preparation, especially if 
a piece of oiled silk or adhesive plaster be applied over the 
part.” — American Journal of Pharmacy. 
