II Classification of Poisons
§ 17. At some future time, with a more intimate knowledge of the way in which each poison acts upon the various forms of animal and vegetable life, it may be possible to give a truly scientific and philosophical classification of poisons—one based neither upon symptoms, upon local effects, nor upon chemical structure, but upon a collation and comparison of all the properties of a poison, whether chemical, physical, or physiological. No perfect systematic arrangement is at present attainable: we are either compelled to omit all classification, or else to arrange poisons with a view to practical utility merely.
From the latter point of view, an arrangement simply according to the most prominent symptoms is a good one, and, without doubt, an assistance to the medical man summoned in haste to a case of real or suspected poisoning. Indeed, under such circumstances, a scheme somewhat similar to the following, probably occurs to every one versed in toxicology:—
A. Poisons Causing Death Immediately, or in a Few Minutes
There are but few poisons which destroy life in a few minutes. Omitting the strong mineral acids, carbon monoxide, carbon dioxide, with the irrespirable gases,—Prussic acid, the cyanides, oxalic acid, and occasionally strychnine, are the chief poisons coming under this head.
B. Irritant Poisons (Symptoms Mainly Pain, Vomiting, and Purging)
Arsenic, antimony, phosphorus, cantharides, savin, ergot, digitalis, colchicum, zinc, mercury, lead, copper, silver, iron, baryta, chrome, yew, laburnum, and putrid animal substances.
C. Irritant and Narcotic Poisons (Symptoms Those of an Irritant Nature, With the Addition of More or Less Pronounced Cerebral Indications)
To this class more especially belong oxalic acid and the oxalates, with several poisons belonging to the purely narcotic class, but which produce occasionally irritant effects.
D. Poisons More Especially Affecting the Nervous System
1. Narcotics (chief symptom insensibility, which may be preceded by more or less cerebral excitement): Opium, Chloral, Chloroform.
2. Deliriants (delirium for the most part a prominent symptom): Belladonna, hyoscyamus, stramonium, with others of the Solanaceæ, to which may be added—poisonous fungi, Indian hemp, lolium temulentum, œnanthe crocata, and camphor.
3. Convulsives.—Almost every poison has been known to produce convulsive effects, but the only true convulsive poisons are the alkaloids of the strychnos class.
4. Complex Nervous Phenomena: Aconite, digitalis, hemlock, calabar bean, tobacco, lobelia inflata, and curara.
§ 18. Kobert’s Classification.—The latest authority on poisons—Kobert—has classified poisons according to the following scheme:—
I. Poisons Which Cause Coarse Anatomical Changes of the Organs
A. Those which specially irritate the part to which they are applied.
1. Acids.
2. Caustic alkalies.
3. Caustic salts, especially those of the heavy metals.
4. Locally irritating organic substances which neither can be classified as corrosive acids nor alkalies, nor as corrosive salts; such are:—cantharidine, phrynine, and others in the animal kingdom, croton oil and savin in the vegetable kingdom. Locally irritating colours, such as the aniline dyes.
5. Gases and vapours which cause local irritation when breathed, such as ammonia, chlorine, iodine, bromine, and sulphur dioxide.
B. Those which have but little effect locally, but change anatomically other parts of the body; such as lead, phosphorus, and others.
II. Blood Poisons
1. Blood poisons interfering with the circulation in a purely physical manner, such as peroxide of hydrogen, ricine, abrine.
2. Poisons which have the property of dissolving the red blood corpuscle, such as the saponins.
3. Poisons which, with or without primary solution of the red blood corpuscles, produce in the blood methæmoglobin; such as potassic chlorate, hydrazine, nitrobenzene, aniline, picric acid, carbon disulphide.
4. Poisons having a peculiar action on the colouring matter of the blood, or on its decomposition products, such as hydric sulphide, hydric cyanide, and the cyanides and carbon monoxide.