The mode in which most narcotic poisons act has been well ascertained: they act on the brain or spine or both by entering the blood-vessels. Hence they are most active when most directly introduced into the blood, that is, when injected into the veins; and when they are applied to an entire membranous surface, their energy is in the ratio of its absorbing power. Thus, when injected into the chest, they act more rapidly than when swallowed. According to the generally received opinion, they are conveyed with the blood to the brain and spine on which they act. But, according to the views of Messrs. Morgan and Addison, they produce on the inner coats of the blood-vessels a peculiar impression, which is conveyed to the centre of the nervous system along the nerves.
The usual symptoms in man and the higher order of animals are giddiness, headache, obscurity or deprivation of the sight, stupor or perfect insensibility, palsy of the voluntary muscles or convulsions of various kinds, and towards the close complete coma. The symptoms of each poison are pretty uniform, when the dose is the same. But each has its own peculiarities, either in the individual symptoms, or in the mode in which they are combined together.
The morbid appearances they leave in the dead body are commonly insignificant. In the brain, where chiefly the physician is led from the symptoms to expect unnatural appearances, the organs are in general quite healthy. Sometimes, however, the veins are gorged with blood, and the ventricles and membranes contain serosity. The blood appears to be sometimes altered in nature; but the alteration is by no means invariable, and sometimes none is remarked at all. Many of the statements to be found in authors on the morbid appearances caused by narcotics are far from being accurate.
Before proceeding to notice the genera of this class in their order, some remarks must be premised on the principal diseases which resemble them in the symptoms and morbid appearances. Of these the only diseases of much consequence are apoplexy, epilepsy, inflammation of the brain, hypertrophy of the brain, inflammation of the spinal cord, and syncopal asphyxia.
Of the Distinction between Apoplexy and Narcotic Poisoning.
Of the Symptoms.—The symptoms of apoplexy are almost exactly the same as those of the narcotic poisons, namely, more or less complete abolition of sense and the power of motion, frequently combined with convulsions. This disease commonly arises from congestion or effusion of blood within the skull; but one variety of it, the nervous apoplexy of older authors, or simple apoplexy of the moderns, is believed to be an affection of the brain, unaccompanied by any recognizable derangement of structure.
Apoplexy and narcotic poisoning may be often distinguished by the following criterions:
1. Apoplexy is sometimes preceded at considerable intervals by warning symptoms, such as giddiness, headache, ringing in the ears, depraved vision, or partial palsy. But it is an error to suppose that warning symptoms always occur; nay, if we may trust the experience of M. Rochoux, they are by no means common: of sixty-three cases which came under his notice nine only had distinct precursory symptoms.[[1625]] Poisoning with narcotics of course has not any precursory symptom except by fortuitous combination. And consequently, if warning symptoms have occurred, the presumption is, that the cause of death is a natural one.
2. Apoplexy attacks chiefly the old. It is not, however, confined to the old. On the trial of Captain Donnellan for poisoning Sir T. Boughton, Mr. John Hunter mentioned that he had met with two instances of death from apoplexy in young women; my colleague Dr. Alison has related to me a similar case; Professor Bernt has described another of a young girl who died apoplectic from extravasation of blood over the whole brain and in the ventricles also;[[1626]] and Mr. Greenhow, a surgeon of London, has even noticed a case of apoplexy from effusion of blood over the surface of the brain in a child two years and a half old.[[1627]] On this subject the treatise of Rochoux supplies excellent information: of his sixty-three cases sixty-one were above thirty years of age, two less than thirty, none younger than twenty.[[1628]] It is plain, therefore, that apoplexy in young people is rare. On the other hand, a great proportion of cases of poisoning with the narcotics when they have been taken intentionally (and such cases are most likely to lead to medico-legal questions), has occurred among the young, especially of the female sex.
3. The next criterion is, that apoplexy occurs chiefly among fat people. But it is here mentioned only that the medical jurist may be cautioned against the belief that it is in all circumstances a correct criterion. Upon this particular Rochoux has furnished some satisfactory data. Among his sixty-three patients thirty were of an ordinary habit, twenty-three were of a thin, meager habit, and ten only were large, plethoric and fat.[[1629]] In receiving this statement, however, it is necessary to consider, that although the vulgar idea, that most apoplectic people are fat, does not apply to persons in the rank of Rochoux’s patients, who were mostly hospital inmates, yet it may apply better to the upper ranks. For the same circumstances which predispose to apoplexy, namely, great strength, vigorous constitution and good digestive powers, likewise predispose to corpulency, so that whenever the condition of life permits the disposition to corpulency to be developed, the connexion of apoplexy with it will appear.