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Dr. J. F. Dana on the existence of 137 
FOR THE ete JOURNAL OF SCIENCE, b¥ 
Ant. XVI. On the evistence of Cantharidin in the Lytt 
- Vittata or Potatoe Fly; by J. Freeman Dana, M. D. 
_ Lecturer on Chemistry &c. . 
TO PROFESSOR SILLIMAN, 
Dear Sir, 
Ir 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 Melie Vesica- 
torius. To this substance Dr. Thomson has given the 
uame Cantharidin, and it is supposed to be the peculiar mat- 
ter which produces vesication. ms begs 
It is well known that some other insects, beside the M. 
Vesicatorius, possess the power of blistering, and that this 
property belongs, in a remarkable degree, to the Lytta Vit- 
tata or Potatoe Fly, so common in this country. This in- 
‘t, 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. 
_ [digested a small quantity, 110 grains of the Potatoe Fly 
in warm distilled water for several days, and the fluid ofa 
ark brown colour was then decanted ; i aaobeied was then 
added, and the operation repeated until no farther action 
which remained some time. The dry extract being di- 
gested in highly rectified alcohol was divided into two por- 
tions, one of which was dissolved by the spirit, the other 
= i ; setts Medical Society, No. 1). 
Part 551 (and Dr Rataniel Dag’ Memolee—Tran-of Cant. Awd 
+t. part I. Dp: 80.9 J : 
Vox, IL.....No. 1. 18 
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