20 
ON CANTHARIDAL COLLODION. 
caliug power of this preparation, render it superior to ordi- 
nary vesicants, while the facility with which irregular sur- 
faces may be evenly coated, so as to secure uniformity of 
action, is a prominent advantage. I have made many ex- 
periments with it, all confirming the statements of Mr. 
Hisch in its favor. It is speedy, convenient and powerful. 
Some improvements, however, might be made in its for- 
mula. The proportion of cantharides is unnecessarily large, 
a tincture made with double the amount of ether, being 
found to vesicate with equal power. 
The contractility — a property possessed by all simple 
solutions of gun cotton in ether — is a serious objection, not 
only causing considerable pain to the sensitive vesicated 
surface : but retarding the action of the preparation. It 
is probably to relieve this that Mr. Hisch recommends the 
application of lard or simple cerate. I had at first sup- 
posed that a sufficient amount of oily or fatty matter existed 
in the cantharides to prevent this unpleasant result ; but 
experience proves the contrary. The addition of Venice 
turpentine to the amount of about one per cent., effectually 
prevents this contraction, and renders the preparation 
perfect. 
Two small circles of equal size upon the arm were coated ; 
the one with collodion, prepared according to M. Hisch's 
formula ; the other, with that modified by the addition 
above suggested. The former contracted powerfully, caus- 
ing a constant painful impression upon the part, and did 
not vesicate until two or three hours after the latter, the 
pain from which was insignificant. 
When the blister is perfectly formed, the film of collodion 
loosens, and curling at the edges, may, by a slight effort, 
be detached without rupturing the membrane beneath, 
whose surface contrasts very favorably with that produced 
by ordinary blistering plaster, which so frequently soils the 
skin. 
If it be simply painted upon I lie skin, and the ether 
