Dr. J, F. Dana on the existence of 137 
FOR THE AMERICAN JOURNAL OF SCIENCE. 
Art. XVI. On the existence of Cantharidin in the Lytta 
Vittata or Potatoe Fly; by J. rerman Dana, M. D- 
Lecturer on Chemistry &c. 
TO PROFESSOR SILLIMAN. 
Dear Sir, 
[r appears from the experiments of Robiquet, mentioned 
by Dr. Thomson in the last edition of his System of Chem- 
istry, that a peculiar substance exists in the Melée Vesica- 
iorius. ‘To this substance Dr. Thomsen has given the 
name Cantharidin, and it is supposedto be the peculiar mat- 
ter which produces vesication. 
It is well known that some other i insects, beside the M. 
Vesicatorius, possess the power of blistering, and that this 
property belongs, m a remarkable degree, to the Lytta Vit- 
tata or Potatoe Fly, so common in this country. This in- 
sect, from the experiments of Dr. Gorham of Boston,* and 
of others, appears to possess vesicating powers ina higher 
degree even than the Spanish Fly, and it became an en- 
quiry of some interest to know whether it contained a sub- 
stance analogous to Cantharidin. 
I digested a small quantity, 110 grains of the Potatoe Fly 
im warm distilled water for several days, and the fluid of a 
dark brown colour was then decanted ; more water was then 
added, and the operation repeated until no farther action 
was exerted, and the last portion of water was poured off 
nearly colourless. ‘The watery infusion had a pungent and 
rather a nauseous taste, and was evaporated by a very gentle 
heat until a dry extract was obtained ; this was of a dark 
brown colour, tough, and_ difficult to cut like urea, and was 
pungent to the taste, leaving an impression on the tongue 
which remained some time. The dry extract being ad 
gested in highly rectified alcohol was divided into two por- 
tions, one of which was dissolved by the spirit, the other 
* See the Medical papers of the Massachusetts Medical Society, No. II. 
Part Il. p. 53; (and Dr. Nathaniel Dwight’s Memoir.—Trans. of Cont. Acad, 
v. 1. part L. p. 99.— Ed.) 
- Vou. 11..,,. No.8. 18 
