230 
ON CANTHARIDIN AND ITS PREPARATIONS. 
coating which cannot be removed, remains in its place, and 
thus protects the sore place, dispensing with the use of 
ointment." This practical communication of Dr. Rapp 
deserves to be universally acknowledged. 
Ether cantharidalis, prepared after my prescription, is 
a suitable constituent of all preparations of cantharidin, and 
is perfectly adapted for preparing the collodium canthari- 
dalis. Instead of dissolving gun-cotton in it, I prefer a 
mixture of equal parts of ether cantharidalis and collodium, 
and rather apply it twice instead of once on the place to be 
blistered. Since the publication of Rapp's method, I em- 
ployed it, prepared after my prescription, in about twelve 
cases, with the best effect. Two scruples of this collodium 
cantharidalis were generally equal to four drachms of the 
common blistering plaster. 
The reason why I have modified Illsch's method of pre- 
paring it, is that his preparation is too strong for children, 
and that the quantity of cantharidin contained in it can 
neither be increased or diminished, whilst, according to my 
prescription, the collodium can be added at discretion ; and 
for children I actually took only one part of ether canthari- 
dalis, and two parts collodium. Finally, I consider my 
method preferable with regard to technical purposes ; ether 
cantharidalis and collodium are always ready, and the 
whole does not require to be purposely prepared, and on 
depending parts of the body the collodium cantharidale 
flows down before it has become dry, and does, therefore, 
not supply, in this case, the place of taffeta vesicans. — 
Pharmaceutical Journal, March 1, 1850. 
