Treatise on Poisons by Sir Robert Christison

the symptoms bears to the last article of food or drink that was taken. I believe that the effects of the common narcotics, in the cases where they prove fatal, begin not later than an hour, or at the utmost two hours, after they are taken; and in a great majority of instances they begin in a much shorter time, namely, in fifteen or thirty minutes. Hence if it can be proved that the nervous symptoms, under which a person died, did not begin till several hours after he took food, drink or medicine, it appears almost, if not absolutely certain, that a narcotic poison cannot have been the cause of death. To some narcotic, or rather narcotico-acrid poisons this rule certainly will not apply, such as the poisonous fungi and spurred rye; which seldom begin to act for several hours, sometimes for not less than a day and a half. Neither will the rule apply to poisoning with the deleterious gases, as their action has no connexion at all with eating or drinking. But these facts do not form a material objection to the rule laid down; because the circumstances under which cases of the kind occur are generally so apparent, as at once to point out their real nature to a careful inquirer. In regard to apoplexy as the disease which resembles most closely the effects of the narcotics, it was formerly stated that this disease is apt to occur soon or immediately after taking a meal (p. 95).[1630] In the greater number of such cases, however, where the meal has been the exciting cause of the disease, the symptoms have begun _immediately_ after, or even during a meal. This is very rarely the case with the symptoms of narcotic poisoning, and never happens in respect to those of the commonest of the narcotics, opium: An interval of 10, 15, 20 or 30 minutes always occurs. The deleterious gases and hydrocyanic acid, with its compounds, are the only familiar narcotic poisons which act more swiftly.