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Full text of "Medical Jurisprudence And Toxicology"

CHAPTER XXVI

IRRITANT POISONS— (Contd.)
II.   ANIMAL POISONS

CANTHARIDES     0

The Spanish fly (Cantharis vesicatoria) or blister-beetle is | to 1 inch
long and J inch broad,, and is distinguished by the shining, metallic green
colour of the head, legs and wing-sheaths. Under these sheaths there are
two thin, brownish, transparent membranous wings. The powder of its dried
body is greyish-brown, and contains shining, green particles. The active
principle is cantharidin, C8Hi20 (CO2) O, the anhydride or lactone of
cantharidic acid, which is a crystalline body, very slightly soluble in water,
but freely soluble in alcohol, ether, chloroform, acetone and fixed oils. It
is a powerful vesicant. The non-official preparations made from it are
Emplastrum cantharidini (Blistering plaster) and Liquor epfepasticus
(Blistering Liquid) containing 0.2 and 0.4 per cent of cantharidin res-
pectively.

The Indian fly (beetle) which yields cantharidin is known as Mylabris
cichorii occurring abundantly in the rainy season in certain parts of North
India and Kashmir. It is 1 inch long and about 1/3 inch broad. Its wing
sheaths are black, marked with three broad, transverse, orange yellow, wavy
bands, which contain scattered black, bristly hairs when viewed under the
microscope.1 Mylabris pustulata is another species which yields cantharidin,
It is found in the fields of cereals and vegetables in the neighbourhood of
Bangalore.2

Symptoms.—Locally applied to the skin, cantharides or cantharidin does
not show any sign for two or three hours, and then produces redness and
burning pain, followed soon by small vesicles, which later tun together to
form one large blister. It may be absorbed by the skin and cause poisoning*

Given internally, this substance produces an intense intolerable burn-
ing pain in the mouth and throat, quickly extending to the stomach and the
whole of the abdomen, and accompanied by difficulty in swallowing, intense
thirst, salivation due to the inflammation of the salivary glands, nausea,
vomiting containing mucus, blood and shreds of mucous membrane mixed
with shining, gregiL-particles, and diarrhoea of bloody stools with tenesmus.
These are followed by pain in the loins, distressing strangury, passage of
scanty urine containing blood and albumin, painful priapism in the male
with swelling and inflammation of the genital organs and frequent seminal
emissions, and abortion in pregnant women. The patient becomes extremely
restless, with laborious respirations, quick pulse and signs of peripheral
failure. In severe cases, headaches, delirium, convulsions and coma usually
precede death.

Occasionally blisters occur in the mouth and other parts of the digestive
tract with which it comes into contact. There are also redness of the eyes
and lachrymation. Blood examination may show haernoconcentration, marked
leucocytosis and primitive white cells in the peripheral blood.

, Fatal Dose,—Twenty-four grains of powdered cantharides (non-official
dose, 1/16 to 2 grain) taken in two doses and an ounce of the non-official
tincture (tinctura cantharidini, dose, 2 to 5 minims) have caused death;
recovery has, however, followed much larger doses. About 1/50 grain8 of

1.   Dutt, Ind. Med. Gaz., March 1922, p. 92.

2.   Iyer and Guha, Jour. Indian Industr. Science, Vol. XIV-A. Part III 1931, p, 81.

3.   C. H. Andrews, Lancet, Sep. 24, 1921, p. 654.