66 SPASM OF THE MUSCLES OF THE HIND-LIMB. 
combination with the other constituents of cantharides ; the 
yellow matter probably being the principal agent in render- 
ing it so. This, then, is the reason why an aqueous infusion 
of the insects contains cantharidin in solution. Cold spirit, 
digested on cantharides, extracts cantharidin ; which it can 
only do by the agency of some of the other principles of 
the flies. It is easily soluble in ether, oils (volatile and 
fixed), and hot spirit of wine ; and from the latter it sepa- 
rates as the liquid cools. Concentrated boiling sulphuric 
acid dissolves cantharidin ; the solution is slightly brown ; 
when diluted with water, it deposits small needle-like crys- 
tals of cantharidin. Boiling nitric and muriatic acids dis- 
solve it without changing colour ; the solutions, by cooling, 
deposit it. Cantharidin is dissolved by potash and soda; 
but when concentrated acetic acid is added to the solution, 
the cantharidin is precipitated. Ammonia is without action 
on it. According to Regnaud it consists of carbon , 6 1 * 68 ; 
hydrogen , 6*04; and oxygen , 32 28. 
(£ 2. Volatile Odorous Oil ? — Orfila asserts, that a volatile 
odorous oil is one of the constituents of the insects. The 
distilled water of cantharides is strongly odorous and milky; 
and its vapour affects the eyes and kidneys like cantharides. 
The active and odorous principles of cantharides reside 
principally in the sexual organs of the animals. Both 
Farines and Zier tell us, that the soft contain more active 
matter than the hard parts. It appears, also, that the poste- 
rior is much more acrid than the anterior portion of the 
body ; and Zier says the ovaries are particularly rich in this 
active matter. If so, it is evident we ought to prefer large 
female to male insects. It is a well-known fact, that the 
odour of these animals becomes much more powerful at 
the season of copulation than at other periods ; and that 
persons sitting under the trees, in which these insects are, 
at this season more particularly, are very apt to be attacked 
with ophthalmia and ardor urinae. 
Bretonneau, in his experiments on Animals, has not found 
any marked aphrodisiac effect produced by cantharidin. 
He found that it rendered the circulation slower, and caused 
fatal lethargy.] 
SPASM OF THE MUSCLES OF THE HIND-LIMB. 
By R. S. Blake, M.R.C.Y.S. 
On the 22nd of December last, I w T as requested to attend 
a black mare, in foal, which had become lame while in the 
