Vesicating Principle of Cantharides. 69 



(17); hence, and by (6), r^= (^^') X (e'^^^ + e-^'^^) + 



a^ — ap' 



— ^ J (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- 



/ t\/A,-t\/A^ ^j. 



comes r=a(^ IL__ ]; .'. -7-= V, the velocity, (at the time ^,) 



=2^X (a'^S-e-'^^) and r-a=|(e'^^+e-'^S)-a=.he 

 space described in the time t. 



Art. VIII. — JVotice of the Vesicating Principle of Cantharides ; in a 

 letter from G. W. Carpenter, dated Philadelphia, July 2d, 1831. 



TO THE EDITOR. 



Dear Sir — I 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 

 is 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 

 eifect intended or being of any benefit whatever to the patient. A 

 piece 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- 

 ced is so exactly circumscribed, that the blister corresponds with the 

 sharpest angles, which may be given to the paper employed. 



One drop is sufficient to make a bhster of the size of a quarter of 

 a dollar. On places where the skin is thicker or more solid than on 

 those which are covered with clothing, and therefore less exposed, it 

 requires that the oil be applied two or three times in the course of an 



