298 ON THE VOLATILITY AND SOLUBILITY OF CANTHARIDIN. 
end of the experiment a minute deposit of microscopic crystals 
less than one thirtieth of a grain, was observed above the flies 
on the sides of the tube. 
e. Two hundred grains of flies were introduced into a two 
ounce retort, which they half filled, adapted to a two ounce re- 
ceiver, and this again connected with a third vessel, The retort 
heated by a mercurial bath, was kept at 225° F., for two hours, 
without any product except a little odorous hygrometric water. 
The heat was then raised to 412° E., when a colorless oily mat- 
ter flowed slowly into the receiver, mixed with water, whilst a 
crystalline matter mixed with oil collected in the neck. This 
crystalline matter mixed with the oil produced vesication when 
applied to the skin. The heat was now rapidly increased so as 
to produce brown vapors, from which was condensed a dark 
colored empyreumatic oil, abundant crystals of an ammoniacal 
salt collected in the tubes and on the sides of the receiver, whilst 
the aqueous liquor in the receiver was strongly ammoniacal. 
Neither the dark oil nor the crystals produced vesication, the 
high temperature having probably decomposed the cantharidin. 
From these experiments it must be admitted that cantharidin 
is less volatile than has been asserted. The effect produced on 
the eye of the pupil of Robiquet who was watching the crystal- 
lization of cantharidin during the evaporation of an ethereal solu- 
tion, may be accounted for by the mechanical action of the dense 
ethereal vapor escaping near his eye, as he watched the process 
with a lens, carrying off some particles of cantharidin ; and 
the readiness with which this principle may be brought me- 
chanically in contact with the skin of the face, during a series 
of experiments, by want of care, will easily account for the oc- 
casional testimony of writers in favor of its volatility at low tem- 
peratures based on that kind of evidence. During the whole of 
the experiments detailed in this paper, the author has not ex- 
perienced any inconvenience to his eyes or face except in two 
instances, once when decomposing cantharides by destructive 
distillation, during which some of the vapors escaped near his 
person, and again where a small capsule containing aqueous ex- 
tract of cantharides was accidentally exposed to high temperature 
over a lamp so as to partially decompose it ; he suffered slight 
pain for a few hours in the conjunctiva of both eyes. 
