OXALIC ACID (_Acid of Sugar_).—This is one of the most important poisons with which we have to deal. From its cheapness and well-known properties it is frequently made use of in cases of suicide, while from its resemblance to Epsom salts it has on several occasions been taken in mistake for that medicine. The smallest dose which is known to have proved fatal is one drachm, which killed a boy æt. sixteen in eight hours. Taylor relates the case of a woman, aged twenty-eight, who was found dead one hour after swallowing three drachms of the crystallized acid. Christison mentions an instance in which one ounce destroyed life in ten minutes, and another case where the same quantity killed a girl in thirty minutes. One example has been recorded where a fatal result ensued probably within three minutes of the acid being swallowed. The poisonous properties of the _Binoxalate of Potash_ (Salt of Sorrel, Essential Salt of Lemons) are due to the oxalic acid it contains. This salt, which exists in the leaves of the wood sorrel (Oxalis acetosella), is sold to bleach straw, remove ink-stains, &c. It is very cheap; is almost as powerful as oxalic acid itself, and gives rise to the same kind of symptoms; it has been taken for the purpose of suicide, as well as in mistake for the bitartrate of potash, or cream of tartar. Oxalate of lime exists in considerable quantity in the leaves and stalks of the common edible rhubarb (Rheum Rhaponticum). It can hardly be considered poisonous. _Symptoms._—The effects of poisoning by oxalic acid are peculiar. When the dose is large (half an ounce or more) and the solution concentrated, it proves very rapidly fatal. It produces a hot burning sensation in the fauces and œsophagus in the act of swallowing, severe burning pain in the stomach, and in most instances immediate vomiting. The vomited matters are strongly acid, of a dirty green or black color, and consist of the contents of the stomach with altered mucus and blood. The remaining symptoms are a sense of constriction or suffocation, lividity of the countenance, great prostration of strength, feeble pulse, cold clammy perspirations, and convulsions, which speedily terminate in death. When a smaller quantity has been taken, much diluted, its corrosive properties are weakened or destroyed, but the nervous symptoms, as cramps and numbness, may be well marked. In cases of recovery the mouth may remain sore for some time, the tongue swollen, the abdomen tender, the stomach very irritable, and there may be troublesome diarrhœa. In two instances there has been loss of voice for several days, owing to the action of the poison on the nervous system. Twitching of the muscles of the face and extremities has also been observed.