Vesicating Principle of Cantharides. 69 
2 / — ~ 
(17); hence, and by (6), (Coe x Cobre + 
a? —ap' 4 ee 
? : n fc) 
9? (18); (17) and (18) are sufficient to find the place of the 
particle at any given time, supposing the time when it is at the ex- 
tremity of a to be known. If p’ is indefinitely diminished, so that 
the particle may be considered as moving in a right line, (18) be- 
— 
a 
comes r=a (2 
; see the velocity, (at the time ¢,) 
VA : ios os - = 
=x (et¥8_ 1a) and r —a=5 Cage des, 
—a=the 
space described in the time f. 
Art. VIII.—WNotice of the Vesicating Principle of Cantharides ; ina 
letter from G.W. Carpenter, dated Philadelphia, July 2d, 1831. 
TO THE EDITOR. 
Dear Sir— beg leave to inform you that I have succeeded in 
separating the vesicating principle of Cantharides, which I have dis- 
solved in oil, and have denominated it “Oil of Cantharidin.” ‘This 
$a new and valuable article, and I have no doubt, from the many 
advantages which it possesses, that it will entirely supersede the com- 
mon mode of blistering. A few drops, rubbed two or three times 
on the part, will effectually draw a full and complete blister, with lit- 
tle or no pain, and without the necessity of applying any thing on it 
to assist the operation. This is certainly preferable to applying a 
Plaster which often gets removed from one place to another, and 
thus frequently vesicates a greater surface than was intended or re- 
quired, and sometimes, from the frequent transition, only partially 
vesicates and causes considerable pain, without having produced the 
effect intended or being of any benefit whatever to the patient. A 
piste of paper which has been made to imbibe this oil, forms an 
excellent blister, which may be accommodated accurately to the 
shape of any part, however irregular. The vesication thus produ- 
ed is so exactly circumscribed, that the blister corresponds with the 
arpest angles, which may be given to the paper employed. 
: dn drop is Sufficient to make a blister of the size of a quarter ol 
*t. On places where the skim is thicker or more solid than on 
Which are covered with clothing, and therefore less exposed, it 
"quires that the oil be applied two or three times in the course of an 
