Page:Treatise on poisons in relation to medical jurisprudence, physiology, and the practice of physic (IA treatiseonpoison00chriuoft).pdf/535

 *toms preceding death is unknown, they may give rise to a suspicion of poisoning generally. But they are at once distinguished by the morbid appearances. A trivial organic derangement may be the occasion of instant death.

The genera comprehended in the class of narcotics are opium, henbane, lettuce-opium, solanum, hydrocyanic acid, and the deleterious gases. Of these genera the last is by no means a pure one, for it includes many gases which act as irritants only; but it is more convenient to consider them together, than to distribute them into separate classes. Some other vegetable substances besides henbane, lettuce-opium, and solanum, possess nearly the same properties; but as they likewise cause irritation, they are arranged more appropriately in the next class, the narcotico-acrids.

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