Treatise on Poisons by Sir Robert Christison

meal_, or rather, soon after food, drink, or medicine has been taken. The occasions on which we eat and drink are so numerous and so near one another, that unless the poison suspected is one which acts with rapidity, it may be difficult to attach any weight to this circumstance. Some poisons rarely produce their effects till a considerable time after they are swallowed; the poisonous mushrooms, for example, may remain in the alimentary canal for several hours or even an entire day and more, before their effects begin; poisonous cheese in like manner may not act for five or six hours,[71] or even a whole day;[72] and that kind of cholera, which is caused in some people by putrid, diseased, and new-killed meat, seldom begins, so far as I have observed, till twelve hours or more after the noxious meal. With regard to the commoner poisons, such as arsenic, corrosive sublimate, the mineral acids, oxalic acid, nux-vomica, and the like, it is a good general rule, that the symptoms, if violent from the beginning, must have begun soon after food, drink, or medicine has been taken. In making inquiries respecting this point, however, care must be taken not to lose sight of certain circumstances which may cause a deviation from the general rule. In the first place, it should be remembered that poisons may be administered in many other ways besides mixing them with articles of food or drink, or substituting them for medicines. They may be introduced into the anus; they have been introduced into the vagina; they have also been introduced by inhalation in the form of vapour; and there can be no difficulty in introducing some of them through wounds. Secondly, another circumstance which may be kept in view is, that, if a person falls asleep very soon after swallowing a poison, especially one of the irritants, the commencement of the symptoms may be considerably retarded, provided it be not one of the powerful corrosives. This statement is not so fully supported by facts as to admit of its being laid down with confidence as a general rule. But from various incidents which have come under my notice it appears not improbable, that sleep does possess the power of putting off for a while the action of some poisons. In particular some instances have occurred to me where arsenic taken at night did not begin to act for several hours, the individual having in the meantime been asleep.[73] The occurrence of so long an interval between its administration and the first appearance of the symptoms is so contrary to what generally happens, that some cause or another must be in activity; and the insensibility of the system during sleep to most sources of excitement seems to supply a sufficient explanation. The slow operation of laxatives during sleep compared with their effects during one’s waking hours, is an analogical fact. A third consideration to be attended to is, that poison may be secretly administered during sleep to a person who lies habitually with his mouth open. This is fully proved by an interesting case which will be noticed under the head of the moral evidence of poisoning. In that particular case the individual immediately awoke, because the poison was concentrated sulphuric acid; but it may admit of question whether a sound sleeper might not swallow less irritating poisons without being awakened. In such circumstances no connexion of course could be traced between the taking of a suspected article and the first appearance of the symptoms.