After death, the odour of prussic acid sometimes exhales, from the body, and is often strongly perceived upon opening the stomach. it is said also to be occasionally discoverable in the blood, and the different cavities. The reader must not confound this odour with that of the oil of bitter almonds. To me the two are quite distinct. The latter smell might lead to the suspicion that hydrocyanic acid had been swallowed in connection with the oil, with which it is generally associated; but it would afford no proof of poisoning with the pure acid. The only marked phenomenon presented, upon post-mortem examination, is a universal venous congestion, proving that the circulation had been arrested in the lungs. The blood is usually found dark, and either fluid or imperfectly coagulated. The left ventricle of the heart is sometimes found contracted, while the remainder of the organ is flaccid and empty, or filled with dark blood. it is said that marks of inflammation exist in the stomach and bowels; but death is often too rapid to permit the establishment of this process, and the redness which has been ascribed to inflammation is probably owing simply to venous congestion

Treatment of Poisoning by Hydrocyanic Acid. Unhappily, the opportunity for interposing remedies is seldom offered, in consequence of the speedy occurrence of death. The prominent indications are to support or restore the respiratory function, and to obviate the debilitating influence of the poison until it shall cease to act. To neutralize or evacuate the acid is also desirable, and should be aimed at when the opportunity is offered; but too often the case ends fatally before the requisite measures can be carried into effect; and the closure of the mouth, and the inability to swallow, are impediments in the way of their application. The most effective measure is probably to dash cold water upon the face, head, or shoulders, or to pour it upon the spine. This, by the shock, rouses the nervous centres, and favours the restoration or continuance of respiration. For the same purpose, carbonate of ammonia, or the aromatic spirit of ammonia, should be applied assiduously to the nostrils; the latter remedy should be administered by the mouth, if the patient can swallow, or by the rectum if he cannot; and stimulation externally should be resorted to by friction and rubefacients. Chlorine has been recommended as an antidote, and, if it can be obtained in time, it may be administered in the form of chlorine water, or perhaps dilute solution of chloride of lime. Another antidote has been recommended, consisting of the mixed sulphates of protoxide and sesquioxide of iron, which must be preceded by a solution of carbonate of potassa. The common sulphate of iron of the shops may be employed, as it really contains the two oxides. An insoluble and inert ferrocyanide of iron or Prussian blue is formed, and the hydrocyanic acid neutralized. The two solutions, the alkaline, namely, and the chalybeate, may be introduced successively into the stomach by injection, if the patient cannot swallow. Should there be any disposition to vomit, it should be favoured by warm drinks. Should respiration have ceased, it must be restored artificially; and efforts may be made to rouse the vanishing action of the heart by means of the electro-magnetic influence.

2. Mode Of Operation

Until lately, it has been supposed that hydrocyanic acid operated, through nervous communication, upon the brain; the rapidity of its action precluding, as it was imagined, the supposition that it could produce its effects through absorption. At present the general opinion tends towards the view, that it operates on the system exclusively through the circulation; and I have myself no doubt that this view is correct. in the first place, it is quite certain that the medicine is not only absorbed, but rapidly so. its odour in the breath of one who has swallowed it, and in the blood and the cavities of the body after death, its discovery in the blood by chemical tests, and the fact that it operates in the same manner to whatever absorbing surface it may be applied, are sufficient proofs to this effect. Secondly, experiments have proved that, however speedy may be its operation, as for example in three or four seconds when inhaled into the lungs of a small animal, yet the movement of the blood is sufficiently rapid to allow time for its absorption and conveyance to the brain. Thirdly, it is not prevented from acting, when applied to the tongue or stomach, by cutting off the nervous communication between these organs and their nervous centres. Lastly, if the circulation of the blood be arrested from the place of its application, it produces no effect. The fact, moreover, that it operates more rapidly when inhaled than when applied in any other mode, whether by the stomach, rectum, or a wound, favours the idea of its absorption; as the air-cells of the lungs afford a readier entrance into the circulation than any other surface; and the distance, by the route of the circulation, thence to the brain is shorter than from any other point of application, even the jugular veins.

The strong acid dropped into the eye, placed upon the tongue, introduced into the stomach or rectum, applied to a wound, or injected into one of the serous cavities, or into the blood of one of the lower animals, usually produces death, and sometimes in a few seconds, so that the action seems almost immediate. The animal generally dies with convulsions.

The heart continues beating after respiration has ceased. Dr. Pereira states that he had examined a considerable number of animals destroyed by hydrocyanic acid, and had met with no instance in which the heart had ceased to beat, when the chest was opened immediately after apparent death. According to the same observer, the voluntary muscles, too, retain their irritability, contracting under the application of galvanism, though the contrary has been noticed by some others. (Mat. Med., 3d ed., p. 1796.)