Most narcotic vegetables owe their poisonous properties to a peculiar principle, probably of an alkaline nature, and slightly different in each. This discovery was made with regard to opium in 1812; and the discovery of the active principle in that drug has been followed by the detection of analogous principles in most narcotics, as well as in many narcotico-acrids.
These principles are generally crystalline, soluble in alcohol and the acids, little soluble in water, free from mineral admixture, and entirely destructible by heat. When purified with the greatest care, they still retain decided alkaline properties; but on account of their number and the low power of neutralization their alkaline nature was long denied; and they have been conventionally styled alkaloids.
In their natural state they exist in combination with various ternary acids, some of which are peculiar; and they are likewise intimately blended, or more probably united chemically, with other inert principles of the vegetable kingdom, particularly resinous and extractive matters, to which they adhere with great obstinacy.
They are all highly energetic, and generally concentrate in themselves the leading properties of the substance from which they are obtained.
The experiments, which have led to the conclusion, that the narcotic poisons act on the brain by entering the blood-vessels, have been repeated with their alkaloids, and have yielded similar results. But the alkaloids are in equal quantities much more energetic than the crude poisons. Their effects indeed are truly formidable, and some well authenticated instances of their action appear hardly less marvellous than the most extravagant notions entertained in ancient times of the operation of poisons. One of them, the principle of nux vomica, which, however, does not belong to the present class, is so active that in all probability a man might be killed with the third part of a grain in less than fifteen minutes.
It is very difficult to detect some of the vegetable alkaloids; and it is fortunate, therefore, that they are rare, and not to be procured but by complex processes.
Chemical analysis does not by any means supply so good evidence of poisoning with the narcotics as it does of poisoning with the irritants. Their chemical properties are not very characteristic, and they are not well developed unless with a larger quantity of the poison than will usually be met with in medico-legal investigations. This remark, however, does not apply universally; and it is probable, that, as organic analysis goes on improving, better and more delicate processes will be discovered.
CHAPTER XXVII.
OF POISONING WITH OPIUM.
To the medical jurist opium is one of the most important of poisons; since there is hardly any other whose effects come more frequently under his cognizance. It is the poison most generally resorted to by the timid to accomplish self-destruction, for which purpose it is peculiarly well adapted on account of the gentleness of its operation. It has also been often the source of fatal accidents, which naturally arise from its extensive employment in medicine. It has likewise been long very improperly employed to create amusement. And in recent times it has been made use of to commit murder, and to induce stupor previous to the commission of robbery. Mr. Burnett, in his work on Criminal Law, has mentioned a trial for murder in 1800, in which the prisoners were accused of having committed the crime by poisoning with opium; and although a verdict of not proven was returned, there is little doubt that the deceased, an adult, was poisoned in the way supposed. A few years ago, a remarkable trial took place at Paris, where poisoning was alleged to have been effected by means of the alkaloid principle of opium; and the prisoner, a young physician of the name of Castaing, was condemned and executed.
In several parts of Britain during the last fifteen years many persons have been brought into great danger by opium having been administered as a narcotic to facilitate robbery; and some have actually been killed. In December, 1828, a conviction was obtained in the Judiciary Court of Edinburgh for this crime, in which instance the persons who had taken the opium recovered. A fatal case, which was strongly suspected to be of the same nature, was submitted to me by the sheriff of this county in 1828; but sufficient evidence could not be procured. In July, 1829, a man Stewart and his wife were condemned, and subsequently executed for the same crime, the person to whom they gave the opium having been killed by it. And about a year afterwards a similar instance occurred at Glasgow, for which a man Byers and his wife were condemned at the Autumn Circuit of 1831.