ON VESICATING APPLICATIONS. 
315 
varnish, to preserve the Cantharidin from the action of the 
atmosphere. I have not had an opportunity of ascertaining 
how far this would prove an effectual preservative. 
But, in order to determine the best form for the application 
of Cantharides, it is necessary to be acquainted with their 
constitution. As early as the year 1803, their examination 
was undertaken by the French chemists, and in the Jinn, de 
Chimie of that year, Permentier gives an account of Dr. 
ThouvenePs analysis of Cantharides, by treating them 
successively with water, alcohol, and ether. In this way he 
obtained, 
Three-eighths of their weight, of yellow extractive matter, 
obtained by water. This was very bitter, and yielded an acid 
liquor by distillation. 
One-tenth ditto, of concrete green oil, subsequently obtained 
by spirit, with the smell of Cantharides, and yielding a sharp 
acid and thick oil on distillation. 
One-fiftieth ditto of a yellow concrete oil, subsequently 
obtained by ether, and analagous to the preceding. 
One-half ditto, of insoluble parenchyma. 
Thouvenel concluded that the vesicating qualities resided 
in the green concrete oil, and that the action on the urinary 
organs was due to one of the acids obtained by distillation. 
Permentier observes in this paper, that Cantharides produce 
a more energetic effect when applied in coarse powder, than 
when finely levigated. Dr. Pereira states, that 
" The active and odorous principles of Cantharides reside 
principally in the sexual organs of the animals. Both Farines 
and Zier tell us, that the soft contain more active matter than 
the hard parts. It appears also that the posterior is much 
more acrid than the anterior portion of the body, and Zier 
says, the ovaries are particularly rich in this active matter. If 
so, it is evident that we ought to prefer large female to male 
insects. It is a well known fact that the odour of these 
animals becomes much more powerful at the season of copula- 
tion than at any other periods, and that persons sitting under 
V 
