ON CANTHARIDIN AND ITS PREPARATIONS. 22 7 
minutely explained its physiological and therapeutical 
effect. 
In this paper I shall give an account of a solution of 
cantharidin which serves as the basis of various blistering 
preparations, and also describe a new vesicating substance 
containing cantharidin, namely, the collodium canthari- 
dale. 
Cantharides when treated with ether, yield the oleum can- 
tharidum viride — consisting of cantharidin, green oil, and 
waxy resin ; the first, by the separation of the two latter 
substances, becomes pure cantharidin. This operation, 
however, is tedious and expensive, and is attended with a 
considerable loss of active matter, without an augumenta- 
tion of the blistering power, but with a great increase of 
price. We employ, therefore, for the purpose of blistering, 
the ol. canth. vir., which is obtained most easily, and in 
the greatest abundance by means of ether. This extract 
readily combines with resins, fat, and collodium, and may be 
admitted into the Materia Medica under the denomination of 
ether cantharidalvs seuvesicans. If applied twice without 
any admixture, by means of a hair pencil, it produces in 
children after one or two hours, and if three times applied 
in adults in three or four hours, abundant blisters, which 
are treated in the same way as those produced by the ordi- 
nary blistering plaster. The other evaporates speedily 
after the application, and the remaining fixed oleum cantha- 
ridin viride operates like the cantharides in substance. 
Preparation of the ether cantharidaiis. 
{& Cantharid. rudit. pulv. part. unam. 
Ether, sulphuric. partes duas. 
Digere per tres dies et exprime. 
In somewhat larger quantity the ol. canth. vir. is obtain- 
ed by employing Real's press, or the displacement aparatus, 
(as Ostermyer does here,) or Mohr's apparatus. The pre- 
parations composed of ether canthar. obtain according to 
the addition of excipients a different form, namely: 
