Numerous experiments on animals have been made to ascertain the rapidity with which prussic acid kills. The late Sir R. Christison found that three drops projected into the eye acted on a cat in twenty seconds, and killed it in twenty more. The same quantity dropped on a fresh wound in the loins acted in forty-five, and proved fatal in one hundred and five seconds. In the cases where death did not occur so rapidly, there were regular fits of violent tetanus; but in the very rapid cases, the animals perished, just as the fit was ushered in, with retraction of the head. In rabbits opisthotonos, in cats emprosthotonos, were the chief tetanic symptoms.
As a proof that the acid acts equally on the brain and spinal cord, may be noticed the presence of coma and tetanus in some cases of poisoning by this substance.
In the experiments on animals certain effects were noticed, which are as follows:
Expulsion of the Fæces and Urine.—In some cases only the fæces, in others the urine alone, was involuntarily expelled; and in some other cases neither the one nor the other was present.
The Shriek or Cry.—This cry, though a common, is by no means a constant symptom.
Convulsions.—These are sometimes present.
Acts of Volition.—Only slight acts are possible; in the case of one of the dogs experimented on by Mr. Nunneley, the animal “went down, came up, and then went down again the whole flight of a steep, winding staircase.”
The Post-mortem Appearances were not well marked in the animals subjected to experiment. In chronic cases, Mr. Nunneley states that both sides of the heart were distended with black blood. The pure acid is stated to completely destroy the irritability of the heart and voluntary muscles, galvanism producing no effect whatever. “In eight experiments on cats and rabbits with the pure acid, the heart contracted spontaneously, as well as under stimuli, for some time after death, except in the instance of the rabbit killed with twenty-five minims, and one of the cats killed by three drops applied to the tongue. In the last two the pulsation of the heart ceased with the short fit of tetanus which preceded death; and in the rabbit, whose chest was laid open instantly after death, the heart was gorged, and its irritability utterly extinct.”
Detection of Hydrocyanic Acid
in Cases of Poisoning
The “Vapour Tests” are those most readily applied to organic mixtures; but in some cases it may be necessary to make a distillation of the suspected substance, in order to isolate the poison.