Substances which, in a moderate dose, occasion a temporary increase of
the actions of the nervous and vascular systems, but which is followed
by a greater depression of the vital powers than is commensurate with
the degree of previous excitement, and which is generally followed by
sleep.
The relative intensity of these primary and secondary effects varies in
the different narcotics,[138] and even in the same narcotic in different
doses; in some cases, especially if the quantity administered be
considerable, the symptoms of diminished sense and action follow so
immediately, that the previous stage of increased action is very
obscure, or not in the least perceptible, while in other cases, the
operation of the substance is more particularly directed towards the
heart and arteries, and syncope succeeds its exhibition. These facts
have led many physiologists to deny the stimulant nature of these
bodies, and to consider their primary operation as one of a depressing
kind, whence they have bestowed upon them the name of SEDATIVES; in
referring to the classification of Cullen and Young, we shall find that
the arrangement of these substances has been directed in strict
conformity with such a view of the subject; but it may be asked, how the
increased excitement and exhilaration which so obviously follow the use
of these bodies, in small doses, can be reconciled with that theory
which considers them as absolutely and primarily sedative? In order to
combat an argument so fatal to his hypothesis, Dr. Cullen summons to his
aid the potent intercession of his tutelar deity, the _Vis Medicatrix_,
a power which he supposes to preside over our living body, and with
anxious vigilance, to resist the invasion of every thing that is
noxious, or hostile to its health and well being; with such assistance
it was not difficult to explain any paradox in physiology, and the
anomalies attending the agency of narcotic medicines were accordingly,
in the school of Cullen, easily reconciled with the views of a favourite
theory. He supposed that whenever a _sedative_ was applied in a moderate
dose, the _Vis Medicatrix_ took the alarm, and excited all the powers of
the system, in order to throw off the noxious application, and that thus
_indirectly_ arose those peculiar symptoms of increased action; but when
the dose was more considerable, he contended that the preserving power
of the system was silenced, and unable to offer any salutary resistance,
and consequently that universal depression immediately followed; but
there is no direct evidence in support of the existence of such a power,
and still less of its influence upon such occasions; it is far more
philosophical to refer the operation of narcotics to a peculiar
stimulating power, remarkable for the extreme rapidity with which it
exhausts the energy of the nervous system. No one will deny the
stimulating powers of alcohol, and yet a very large draught of this
liquor will occasion extreme exhaustion without the occurrence of any
signs of previous excitement; nor will any one be disposed to question
the depressing influence of opium, and yet small doses have enkindled
excitement and sustained the powers of life, under circumstances of
extreme and alarming exhaustion.[139]
From the celerity with which narcotics produce their effects, it is
reasonable to suppose that they act upon the nervous system through the
sympathetic relations of the stomach, although in some instances it is
highly probable that these bodies are actually absorbed into the
circulation; I am inclined to think that this occurs with opium, as
death is accelerated in cases of persons poisoned by it, by the adoption
of those measures which are best calculated to promote its absorption:
(_see Opium_.) A still more striking proof is furnished by the fact of
opium, when externally applied to ulcers, producing all its
constitutional effects, such as costiveness, head-ache, nausea, &c.
Whether the effects of spirituous potations are to be attributed to the
introduction of alcohol into the blood, or to the sympathies existing
between the stomach and brain, is still a question of doubt. Dr.
Cooke[140] relates a case, on the authority of Sir A. Carlisle, of a
person who was brought dead into the Westminster Hospital, in
consequence of having drank a quart of gin for a wager, and that upon
examination, a considerable quantity of a limpid fluid was found within
the lateral ventricles of the brain, _distinctly impregnated with gin_.
I very well remember the case, for it occurred during the period that I
held the situation of Physician to that hospital, but it is very
doubtful whether such an absorption occurs under ordinary circumstances.
We well know the facility with which certain odorous bodies enter the
circulation, and are developed in distant organs; it is therefore very
possible that the apparent odour of the gin, which has been sometimes
recognized in the secretions, may depend upon the presence of the
flavouring ingredients, independent of the alcohol?
At one period, substances supposed to possess narcotic virtues were
placed about the bed to obviate watchfulness; the plant _Anethum_, or
_Dill_, was very commonly suspended over the head for such a purpose,
while in modern times the _Hop_ has been introduced into the pillow.
In concluding the history of Narcotics, it may be observed, that there
is, perhaps, no class of medicinal bodies, the individuals of which are
less disposed to bend and conform to an artificial arrangement; each
would seem to have its own particular mode of operation, and to affect
sensibility in its own peculiar manner; and hence the practitioner will
often find that, after the failure of one narcotic, the administration
of another will induce sleep.