Medical properties and uses. - Hydrocyanic acid, when taken into the stomach, in a large dose, acts as an instantaneous and most powerful sedative, destroying completely the nervous energy and the irritability of the body, and consequently extinguishing life: but in an animal thus killed, the action of the heart continues for some time after the animal has apparently ceased to live. The observation of this curious fact led Professor Brera, in 18091, to administer hydrocyanic acid as a remedy in pulmonary inflammation; and he found that it quickly subdued the violence of the disease, "without having any recourse to more than one preliminary bleeding."

Medica dell' Imperiale R. Universita di Padova, ne' sei anni scolastici, 1809 1815."

British practitioners, however, were altogether unacquainted with this remedy, until after Dr. Majendie published his first essay on this subject in 1815; when Dr. Granville, through the medium of the London Medical Repository, directed their attention to its powers; and I refer those who are desirous of tracing the introduction of hydrocyanic' acid into use, as a medicinal agent, to his treatise subsequently published on the internal use of this acid.1

Hydrocyanic acid, internally exhibited, is a remedy of great efficacy in spasmodic coughs of every description, particularly those of asthma, chronic bronchitis, and hooping-cough. It has also been employed with success in palpitations of the heart.2 In my own practice, I have witnessed its powers in that affection of the trachea which is often mistaken for phthisis pulmonalis, and is not less fatal. In true tubercular phthisis, my own experience does not enable me to say much in favour of this acid. It nevertheless sometimes diminishes the violence and the frequency of the cough, and allays the dyspnoea and the difficulty of expectoration. It has been found extremely useful in the treatment of those epidemic catarrhs with which this country is occasionally visited; and no remedy is so well adapted as an adjunct to tonics, for removing those dyspeptic affections which are attended with irritability of the stomach, and accompanied with heat and soreness of the tongue. In these cases it reduces the morbid irritability of the stomach, and enables the juices of that organ to be more slowly secreted, and of a more healthy character.3 Its beneficial effects in asthma and in hooping-cough are also well established.

M. Heller recommends it in aneurism of the heart and aorta.4 Cases are also on record in which this acid has proved serviceable in the treatment of painful and difficult menstruation, floodings, haemoptysis, and nervous diseases. It certainly is a very powerful sedative; and may be employed in all cases in which sedatives and narcotics are indicated, with decided advantage.

1 Treatise on the internal Use of Hydrocyanic Acid, etc. 2d edition, London, 1820.

2 London Med. and Phys. Journ. Nov. 1823.

3 Dr. Elliotson published a small volume containing the result of his practice with hydrocyanic acid in dyspepsia; and has stated that accident led him to try the powers of the medicine in this class of diseases. Respect for my own character obliges me to say, that nothing could surprise me more than this statement of Dr. Elliotson; as he acknowledges having read the first edition of Dr. Granville's treatise, which contains a letter from me, dated 20th February, 1819, stating my opinion as to the utility of this acid, in dyspepsia, and explaining the modus operandi of the remedy, previously to his having employed it!

4 Vide Traite" de la Necessite de ne point insister sur l'Usage interieur des Excitas dans l'Empoisonnement par l'Acide Hydrocyanique. Par II. S. Heller. Paris, 1824.

As a local remedy, hydrocyanic acid is the only application which can be depended on for allaying the itching and tingling so distressing in impetiginous affections. I have employed it with unvarying success in these complaints, and having published my observations 1, its value has been determined in the hands of others. I have found it useful, also, in combination with small doses of bichloride of mercury in acne rosacea, and several other cutaneous diseases.

The dose of hydrocyanic acid is from ij. to viij. It may be administered in distilled water, or in almond emulsion, or in infusion of cinchona bark, as circumstances require. When an over-dose has been taken, its deleterious effects are best counteracted by inhaling largely diluted chlorine, by taking hot brandy and water, the ammoniated tincture of iron, and, by artificial respiration. M. Heller recommends bleeding, am-moniacal frictions, and acidulated drink; but more reliance is to be placed on stimulants. As a local application it may be used in the form of lotion, in the proportion of a fluid drachm to five fluid ounces and a half of distilled or of rose water; or as a cataplasm composed of crumb of bread, soaked in a solution of f 3jss. of the acid in f j. of distilled water. It is incompatible in prescriptions with nitrate of silver, the salts of iron, and the mineral acids.

Although the instantaneous power of hydrocyanic acid, in destroying animal life, when it is taken in doses sufficiently large to operate as a poison, may, perhaps, always prevent medical art from proving beneficial in such cases; yet it is of importance to be able to ascertain in judicial enquiries, relative to suicide or to murder, that this acid has been administered as a poison. This may be done if the animal be opened from eighteen to forty-eight hours after death. Collect the blood contained in the ventricles of the heart, a portion of the contents of the stomach, and of any fluid that may be found in the head, the chest, or the abdomen; agitate the mixture for some time with distilled water, and filter the liquid, and distil at a low temperature. To a small quantity of the distilled liquid, add a few drops of a solution of pure potassa in alcohol; then add a few drops of a solution of protosulphate of iron; and if a reddish precipitate of the colour of burnt terra Siena now fall down, which on the addition of a little sulphuric acid changes to a bluish green, and gradually, on exposure to the atmosphere, becomes a beautiful blue, we may certainly pronounce that the death of the individual has been occasioned by hydrocyanic acid.

Another mode of testing is that which M. Lassaigne has proposed. Suppose a practitioner is called to examine the body of a person who has been poisoned by hydrocyanic acid. The stomach is first to be examined entire, to ascertain whether the odour of that acid is perceptible in it; after which it is to be cut in pieces under distilled water, slightly acidulated with sulphuric acid, and a portion of it distilled with an equivalent proportion of the water, until one eighth of the liquid has passed into the receiver. That liquid is to be rendered slightly alkaline with potassa, then a few drops of a solution of sulphate of copper are to be added to a small portion of it, and afterwards a sufficient quantity of hydrochloric acid to redissolve the excess of the oxide of copper. The liquid will appear more or less milky according to the quantity of hydrocyanic acid present. This test will detect 1/20000 of hydrocyanic acid in solution in water.1 The presence of the acid in the stomach may be thus detected two or three days after death : but after that period its volatility dissipates it, and it is also decomposed.

1 Vide Medical and Physical Journal, Feb. 1822.