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.

III. POISONS WHICH KILL WITHOUT THE PRODUCTION OF COARSE ANATOMICAL CHANGE.

1. Poisons affecting the cerebro-spinal system; such as chloroform, ether, nitrous oxide, alcohol, chloral, cocaine, atropine, morphine, nicotine, coniine, aconitine, strychnine, curarine, and others.

2. Heart Poisons; such as, digitalis, helleborin, muscarine.

IV. POISONOUS PRODUCTS OF TISSUE CHANGE.

1. Poisonous albumin.

2. Poisons developed in food.

3. Auto-poisoning, e.g. uræmia, glycosuria, oxaluria.

4. The more important products of tissue change; such as, fatty acids, oxyacids, amido-fatty acids, amines, diamines, and ptomaines.

§ 19. I have preferred an arrangement which, as far as possible, follows the order in which a chemical expert would search for an unknown poison—hence an arrangement partly chemical and partly symptomatic. First the chief gases which figure in the mortality statistics are treated, and then follow in order other poisons.

A chemist, given a liquid to examine, would naturally test first its reaction, and, if strongly alkaline or strongly acid, would at once direct his attention to the mineral acids or to the alkalies. In other cases, he would proceed to separate volatile matters from those that were fixed, lest substances such as prussic acid, chloroform, alcohol, and phosphorus be dissipated or destroyed by his subsequent operations.

Distillation over, the alkaloids, glucosides, and their allies would next be naturally sought, since they can be extracted by alcoholic and ethereal solvents in such a manner as in no way to interfere with an after-search for metals.

The metals are last in the list, because by suitable treatment, after all organic substances are destroyed, either by actual fire or powerful chemical agencies, even the volatile metals may be recovered. The metals are arranged very nearly in the same order as that in which they would be separated from a solution—viz., according to their behaviour to hydric and ammoniac sulphides.

There are a few poisons, of course, such as the oxalates of the alkalies, which might be overlooked, unless sought for specially; but it is hoped that this is no valid objection to the arrangement suggested, which, in greater detail, is as follows:—

A.—POISONOUS GASES.

  1. Carbon monoxide.
  2. Chlorine.
  3. Hydric sulphide.

B.—ACIDS AND ALKALIES.

  1. Sulphuric acid.
  2. Hydrochloric acid.
  3. Nitric acid.
  4. Potash.
  5. Soda.
  6. Ammonia.
  7. Neutral sodium, potassium, and ammonium salts.

In nearly all cases of death from any of the above, the analyst, from the symptoms observed during life, from the surrounding circumstances, and from the pathological appearances and evident chemical reactions of the fluids submitted, is put at once on the right track, and has no difficulty in obtaining decided results.

C.—POISONOUS SUBSTANCES CAPABLE OF BEING SEPARATED BY DISTILLATION FROM EITHER NEUTRAL OR ACID LIQUIDS.

  1. Hydrocarbons.
  2. Camphor.
  3. Alcohols.
  4. Amyl-nitrite.
  5. Chloroform and other anæsthetics.
  6. Carbon disulphide.
  7. Carbolic acid.
  8. Nitro-benzene.
  9. Prussic acid.
  10. Phosphorus.

The volatile alkaloids, which may also be readily distilled by strongly alkalising the fluid, because they admit of a rather different mode of treatment, are not included in this class.

D.—ALKALOIDS AND POISONOUS VEGETABLE PRINCIPLES SEPARATED FOR THE MOST PART BY ALCOHOLIC SOLVENTS.

DIVISION I.—Vegetable Alkaloids.
  1. Liquid volatile alkaloids, alkaloids of hemlock, nicotine, piturie, sparteine, aniline.
  2. The opium group of alkaloids.
  3. The strychnine or tetanic group of alkaloids—strychnine, brucine, igasurine.
  4. The aconite group of alkaloids.
  5. The mydriatic group of alkaloids—atropine, hyoscyamine, solanin, cytisine.
  6. The alkaloids of the veratrines.
  7. Physostigmine.
  8. Pilocarpine.
  9. Taxine.
  10. Curarine.
  11. Colchicin.
  12. Muscarine and the active principles of certain fungi.

There would, perhaps, have been an advantage in arranging several of the individual members somewhat differently—e.g., a group might be made of poisons which, like pilocarpine and muscarine, are antagonistic to atropine; and another group suggests itself, the physiological action of which is the opposite of the strychnos class; solanin (although classed as a mydriatic, and put near to atropine) has much of the nature of a glucoside, and the same may be said of colchicin; so that, if the classification were made solely on chemical grounds, solanin would have followed colchicin, and thus have marked the transition from the alkaloids to the glucosides.

DIVISION II.—Glucosides.
  1. The digitalis group.
  2. Other poisonous glucosides acting on the heart.
  3. Saponin.

The glucosides, when fairly pure, are easily recognised; they are destitute of nitrogen, neutral in reaction, and split up into sugar and other compounds when submitted to the action of saponifying agents, such as boiling with dilute mineral acids.

DIVISION III.—Certain Poisonous Anhydrides of the Organic Acids.
  1. Santonin.
  2. Mezereon.

It is probable that this class will in a few years be extended, for several other organic anitrogenous poisons exist, which, when better known, will most likely prove to be anhydrides.

DIVISION IV.—Various Vegetable Poisonous Principles not admitting of Classification under the previous Three Divisions.

Ergot, picrotoxin, the poison of Illicium religiosum, cicutoxin, Æthusa cynapium, Œnanthe crocata, croton oil, savin oil, the toxalbumins of castor oil and Abrus.

The above division groups together various miscellaneous toxic principles, none of which can at present be satisfactorily classified.

E.—POISONS DERIVED FROM LIVING OR DEAD ANIMAL SUBSTANCES.

DIVISION I.—Poisons Secreted by the Living.
  1. Poisonous amphibia.
  2. Poison of the scorpion.
  3. Poisonous fish.
  4. Poisonous insects—spiders, wasps, bees, beetles, &c.
  5. Snake poison.
DIVISION II.—Poisons formed in Dead Animal Matters.
  1. Ptomaines.
  2. Poisoning by putrid or changed foods—sausage poisoning.

F.—THE OXALIC ACID GROUP.

G.—INORGANIC POISONS.

DIVISION I.—Precipitated from a Hydrochloric Acid Solution by Hydric Sulphide—Precipitate, Yellow or Orange.
DIVISION II.—Precipitated by Hydric Sulphide in Hydrochloric acid Solution—Black.
DIVISION III.—Precipitated from a Neutral Solution by Hydric Sulphide.
DIVISION IV.—Precipitated by Ammonia Sulphide.
DIVISION V.—Alkaline Earths.