Summary of symptoms exhibited by various poisons: (1) Sudden death—(2) Insensibility—(3) Vomiting—(4) Action on the eye—(5) Convulsions—(6) Chronic poisoning. Alkaloids, chemically and physiologically—Processes for their detection—Necessity for keeping the extracts separate—Dragendorff’s process—Dr. Guy’s sublimation process—Effects on animals—Doubtful value of this test—Preparation and effects of reagents: (1) Mayer’s—(2) Potassium tri-iodide—(3) Sonnenschein’s test—(4) Bismuth—(5) Phosphotungstic acid—(6) Picric acid—(7) Animal charcoal—(8) Platinic chloride—(9) Tannin or tannic acid—(10) Phospho-antimonic acid—(11) Silico-tungstic acid—(11) Auric, palladium and mercuric chlorides—Ptomaines or cadaveric alkaloids; difficulties raised by their discovery—Principles to be observed in analysing.
Before proceeding to a separate examination of the poisons used in the following trials, it will be advisable to take a general view of poisons, specially noticing those that we have selected as the most important legally. They do not admit, perhaps, of accurate classification, but inasmuch as the manner of death and symptoms are usually the most available indication as to the nature of the poison that has acted, the following arrangement will be serviceable. The heads indicate the most prominent symptom:
I. Sudden Death.—Large quantities of any poison might be rapid in fatal result, but the sudden poisons proper are:—concentrated sulphuric, nitric, and hydrochloric acids; poisonous gases and vapours, such as carbonic acid and sulphuretted hydrogen (see Casper’s Forensic Medicine, Case CCXLI.), carbonic oxide, arseniuretted and antimoniuretted hydrogen, and certain rare organic compounds, as kakodyl, &c.; strychnia sometimes, oxalic acid in large doses, chloroform under certain circumstances. But beyond all others, the quickest of poisons is hydrocyanic or prussic acid.
II. Insensibility, generally following nervous excitement. Morphia and opium; henbane (Hyoscyamus); stramonium; belladonna; nicotine (tobacco); darnel (lolium temulentum); hemlock (Conium maculatum); water hemlock (Œnanthe crocata); fool’s parsley (Æthusa cynapium), [Dr. J. Harley shows that this is not so poisonous as believed: see St. Thomas’s Hospital Reports, x. 25]; Indian hemp (Cannabis indica); Woody Nightshade (Solanum dulcamara); Solanum nigrum; the berries of Potato (Solanum tuberosum); Lobelia inflata: Foxglove (Digitalis); cocculus indicus; certain fungi (notably Amanita muscaria); chloroform; chloral; butylchloral —“croton chloral”): amylene; methylene dichloride; sulphuretted hydrogen; carbonic oxide; and many other substances usually classed as narcotics.
III. Vomiting.—Irritant poisons, such as acids, alkalies, alkaline salts in considerable doses (even common salt has proved fatal: see Christison[1]); most soluble compounds of the heavy metals (especially antimony, arsenic, zinc, and copper); certain vegetal alkaloids (from colchicum, laburnum, yew, savin, ipecacuanha, capsicum, pepper, ergot, many species of Ranunculaceæ, the Hellebores, and some fungi); cantharides, turpentine, and essential oils, &c. Pain in the digestive organs, purging, and general inflammation are commonly present. Most of the medicinal purgatives will produce sickness and vomiting if given in overdoses; of course unwholesome food or disease may frequently be the cause.
IV. Action on the Eye.—Opium and morphia, calabar bean, aconite (?), and strychnia, contract the pupil: belladonna, henbane, tobacco, stramonium, digitalis and hemlock, dilate the pupil. The effect is often temporary, and sometimes is reversed after a time. It is a valuable indication in after-experiments on animals.
V. Convulsions.—Strychnia, brucia, and some fungi: but this symptom is by no means confined to these, and may even result as tetanus, from disease or irritants (see Trial of Palmer). Morphia, in rare cases, has also caused it.
VI. Chronic Poisoning, prostration and wasting. Antimony, mercury, and lead in small repeated doses. With the two latter, but more especially with lead, there is a blue line at the edge of the gums; constipation and colic, paralysis and trembling of the limbs. As lead frequently occurs as an impurity in food, and also may be absorbed by those working with it, these symptoms may be often accidental. Mercury also is given, less than of old, it is true, but still systematically by some, as a regular course in syphilis, &c.: also to children in teething powders. Antimony has been almost abandoned in medicine, from its depressant effect. In these cases, motive, amount, and necessity of dose, and right to administer, must be considered before wilful poisoning can be proved. The analysis, therefore, must be strictly quantitative, which is fortunately tolerably easy.
The above summary is by no means perfect, since there are minor differences in each class, which may sometimes rise into such prominence as to confuse the classification. But in medical evidence on the individual poisons of which we treat, those physiologically resembling them in action are always most heard of at the trial, and questions are asked whether this or that may not produce the same symptoms; and hence it is well to direct attention to the analogues of our types.
The primary idea of an alkaloid is derived from its resemblance to an alkali. Alkaloids are often called also “Organic Bases.” Their names terminate in—ia or ine.[2] They are more or less alkaline to test paper, and combine with acids to form salts which are neutral in reaction and often crystallizable. Only a few of the alkaloids are liquid and easily volatile, but almost all can be volatilized by careful heating at definite temperatures, giving in many cases a sublimate of characteristic appearance under the microscope, either of crystals, globules, or a mere film. In a free state, the alkaloids are very slightly soluble in water, but soluble in alcohol, and generally in ether and chloroform. Some are soluble in benzine, others in amylic alcohol, petroleum spirit, acetic ether, &c. On a judicious use of these various solvents depend the different processes of isolation, among which Dragendorff’s is the most complete, but so complicated that it is rarely used in its entirety. Fortunately there is generally a clue more or less definite to the probable poison administered, enabling a shorter and quicker method to be adopted. For further details as to these processes see Blyth’s Manual of Practical Chemistry. The sulphates, chlorides, and acetates of the alkaloids are generally soluble in water; if ammonia or potash be added to the solution, a precipitate (usually crystalline) of the free alkaloid occurs if the solution be of moderate strength.