The classification of poisonous plants according to their effects is a somewhat difficult process, since more than one prominent symptom may be produced by the same plant. Two classifications, however, may be given as examples, the first that of Blyth, and the second that of A. B. Smith. These must be regarded as essentially applicable to human beings, though serving more or less as a guide in case of poisoning of farm live-stock.

Blyth’s Classification (after Pammel).

A.—Poisons causing death immediately or in a few minutes: Prussic acid, cyanides, oxalic acid, and occasionally strychnine.

B.—Irritant Poisons, with symptoms chiefly pain, vomiting, and purging: Ergot, digitalis, colchicum, yew, laburnum.

C.—Irritant and Narcotic Poisons, with symptoms of an irritant nature, with more or less cerebral indications: Oxalic acid or oxalates.

D.—Poisons more especially affecting the Nervous System:

1. Narcotics.—Symptoms: insensibility, which may be preceded by more or less cerebral excitement. Opium.

2. Deliriants.—Delirium, for the most part, a prominent symptom: Belladonna, hyoscyamus, stramonium, and other SolanaceÆ, Lolium temulentum, Oenanthe crocata, poisonous fungi.

3. Convulsives.—Almost every poison has been known to produce convulsive effects, but the only true convulsive poisons are the alkaloids of the strychnine class.

4. Complex Nervous Phenomena.—Aconite, digitalis.

A. Bernhard Smith’s Classification.

A.—Poisons acting on the Brain.

1. Narcotics.—Symptoms: Giddiness; dimness of sight; contracted pupils; headache; noises in the ears; confusion of ideas, and drowsiness, passing into insensibility.

British Plants included: Papaver somniferum.

2. Deliriants.—Symptoms: Spectral illusions; delirium; dilated pupils; thirst and dryness of the mouth; incoordination. Occasionally, though rarely, there are paralysis and tetanoid spasms.

British Plants included: Datura Stramonium, Hyoscyamus niger, Solanum Dulcamara, Solanum nigrum, Atropa Belladonna, Lolium temulentum.

3. Inebriants.—Symptoms: Excitement of cerebral functions and of the circulation; loss of power of coordination and of muscular movements, with double vision; leading to profound sleep and deep coma.

British Plants included: Pinus pinaster, Pinus larix, Artemisia maritima, Artemisia Absinthium.

B.—Poisons acting on the Spinal Cord.

Convulsives.—Symptoms: Clonic (intermittent) spasms, extending from above downwards. Opisthotonos very violent; but trismus (lockjaw) rare. Swallowing spasmodic. Death, usually, in less than three hours, or rapid recovery.

British Plants included: none.

C.—Poisons acting on the Heart.

1. Depressants.—Symptoms: Vertigo; vomiting; abdominal pain; confused vision; convulsions; occasional delirium; paralysis; syncope; sometimes asphyxia.

British Plants included: Conium maculatum, Cytisus Scoparius.

2. Asthenics.—Symptoms: Numbness, and tingling in the mouth; abdominal pain; vertigo; vomiting; purging; tremor; occasional delirium; paralysis; dyspnoea, ending in syncope.

British Plants included: Prunus laurocerasus, (Phaseolus lunatus—imported cattle food), Lathyrus aphaca, Rumex Acetosa, Aconitum Napellus, Actaea spicata, Delphinium consolida, Digitalis purpurea, Convallaria majalis, Colchicum autumnale.

D.—Vegetable Irritants.

1. Purgatives.—Symptoms: Abdominal pain; vomiting and purging; cramps; strangury and tenesmus, followed by collapse, and sometimes accompanied by drowsiness, and slight nervous symptoms.

British Plants included: Sambucus nigra, Sambucus Ebulus, Helleborus viridis, Helleborus foetidus, Caltha palustris, Linum catharticum.

2. Abortives.—Symptoms: Nausea; vomiting; stupor; polyuria; sometimes tenesmus. Abortion may or may not occur; coma.

British Plants included: Juniperus Sabina (cultiv. in Britain), Claviceps purpurea; Ruta graveolens (cultiv. in Britain).

3. Irritants with Nervous Symptoms.—Symptoms: Abdominal pain; vomiting and purging; dilated pupils; headache; tetanic spasms; occasional convulsions; sometimes rapid coma.

British Plants included: Oenanthe crocata, Oenanthe Phellandrium, Oenanthe fluviatilis, Cicuta virosa, Aethusa Cynapium, Sium angustifolium, Taxus baccata, Cytisus Laburnum, Paris quadrifolia, Mercurialis perennis.

4. Simple Irritants.—Symptoms: Burning pain in the throat and stomach; thirst; nausea; vomiting; tenesmus; purging; dysuria; dyspnoea and cough occasionally. Death through shock; convulsions; exhaustion; or starvation due to injury to throat or stomach.

British Plants included: Arum maculatum, Daphne Laureola, Daphne Mezereum, Narcissus moschatus, Narcissus poeticus, Scilla bifolia, Galanthus nivalis, Hyacinthus nonscriptus, Fritillaria meleagris, Clematis Vitalba, Anemone nemorosa, Anemone appenina, Ranunculus aquatilis, R. Flammula, R. Ficaria, R. auricomus, R. sceleratus, R. acris, R. bulbosus, Aquilegia vulgaris, Bryonia dioica, Ligustrum vulgare, Asarum europÆum, Saponaria officinalis, Valeriana officinalis, Agrostemma Githago, Doronicum Pardalianches, Impatiens noli-me-tangere, Erysimum cheiranthoides, Cynoglossum officinale, Arctostaphylos Uva-ursi, Tamus communis, Euonymus europÆus, Rhamnus catharticus, Glaucium luteum, Roemeria hybrida, Papaver Rhoeas, Chelidonium majus, Sedum acre, Sedum album, Drosera rotundifolia, Linaria vulgaris, Iris Pseud-acorus, Iris foetidissima, Buxus sempervirens, Crocus sativus, Euphorbia Peplis, E. pilosa, E. Helioscopia, E. platyphylla, E. hiberna, E. portlandica, E. Paralias, E. Peplus, E. exigua, E. Lathyris, E. amygdaloides, Urtica dioica, U. urens, U. pilulifera, Viscum album, Lepidium latifolium.

5. Simple Irritants when taken in Large Quantities.—Symptoms: Burning pain in throat and stomach, vomiting; purging; difficulty in swallowing. Recovery usual.

British Plants included: Sinapis alba, and S. nigra.