Irritant poisons give rise to pain in the stomach and bowels, faintness and sickness, and purging with tenesmus. The evacuations are often tinged with blood, the pulse is feeble and irregular, and the skin cold. Many of the substances of this class from irritating the tissues with which they come in contact, produce a severe burning sensation in the mouth and œsophagus, as well as in the stomach. The degree of local destructive action produced will of course vary in proportion to the amount of the vehicle with which the noxious agent may be diluted. Irritants cause death by inducing collapse or convulsions, or by exciting severe inflammation; or, after a variable interval, by leading to stricture of the œsophagus. The diseases which most resemble the action of irritants are, malignant cholera, severe diarrhœa, colic, gastritis, enteritis, rupture of the stomach or intestines, and obstruction of the bowels, mechanical or otherwise.
The symptoms of apoplexy, epilepsy, and uræmia bear a resemblance to those caused by some of the poisons of the neurotic class. Others give rise to delirum with spectral illusions or convulsions. Sometimes there is tetanus, sometimes coma or syncope. Diseases of the brain and spinal cord, likely to be confounded with these, are often very insidious in their progress, and hence may suddenly give rise to suspicious symptoms. The history, mode of attack, &c., will generally negative any suspicion of poisoning.
[I.—CORROSIVES.]
[CHAPTER VI.]
THE CONCENTRATED MINERAL ACIDS.
The first division of the Corrosive consists of the Strong Mineral Acids. In this chapter we have to review the effects, &c., of the acids commonly encountered, which are Sulphuric Acid, Nitric Acid, Hydrochloric Acid, or a mixture of two or more of them.
Sulphuric Acid (Oil of Vitriol).—This heavy, oily looking liquid is met with in two states, concentrated and diluted; and being extensively employed in commerce and manufactures is much more frequently used as a poison than the other mineral acids. Many infants and young children have been poisoned by it; occasionally also men, under the influence of drink. The acid is not unfrequently thrown over the person, either to disfigure the features or to destroy the clothes. The parts of the body with which it is brought into contact are stained at first of a white, and afterwards of a dark brown or black color. The smallest fatal dose of concentrated acid recorded, in the adult, is one drachm; but recovery has taken place after as much as two ounces. But it must be understood that the acid proves fatal mainly by its power of corrosion, so that a small dose of the concentrated acid is more dangerous than is a much larger dose of it in the dilute form. The average period at which death occurs is from sixteen to twenty-four hours; but on the other hand, death may not occur for months, and may only follow the organic changes induced by cicatrization following the swallowing of the acid, or the malnutrition following its destructive action on the coats of the stomach.
Tests.—It is not within the province of these Memoranda to treat of the various processes by which poisons are to be detected; for to make a trustworthy analysis requires the skill of a professed chemist, whose assistance should be allowed in these medico-legal investigations. Where the character of a dead man or the life of a supposed criminal is at stake there must be no chance of error. The ordinary tests will, however, be briefly described, if only to help the physician to treat the case more satisfactorily than he could do by merely guessing that an irritant or narcotic had been employed: