_Of the history and the various opinions concerning the cause of this
Disorder._
In order to convey a distinct idea of the subject of the following
pages, I shall, according to the old custom of medical authors, begin
with the etymology of it.
Altho’ we have reason to believe, as will afterwards appear, that this
Disease was known long before the Greek language, yet, the earliest
account we have of it, is from the Greek authors, who call’d it
Εφιαλτης, and the Romans nam’d it Incubus, both which words partly
express its effects.
In our language it is generally known by the name of the NIGHT-MARE;
which strange term probably arose from superstitious notions which the
British had, and perhaps still have, of it. How it first obtain’d this
odd appellation, I never could learn, nor is it material to know, since
that name is sufficient to distinguish it from every other Disease.
The Night-mare generally seizes people sleeping on their backs, and
often begins with frightful dreams, which are soon succeeded by a
difficult respiration, a violent oppression on the breast, and a total
privation of voluntary motion. In this agony they sigh, groan, utter
indistinct sounds, and remain in the jaws of death, till, by the utmost
efforts of nature, or some external assistance, they escape out of that
dreadful torpid state.
As soon as they shake off that vast oppression, and are able to move
the body, they are affected with a strong Palpitation, great Anxiety,
Languor, and Uneasiness; which symptoms gradually abate, and are
succeeded by the pleasing reflection of having escap’d such imminent
danger. All these symptoms I have often felt, and hope, that whoever
has had, or may have, this Disease, will readily know it by this
description, which I have not only taken from my own feelings, but from
the observations of many of my acquaintances, who were also afflicted
with it, and from the records of the antient observators.
Before I enter into an enquiry concerning the cause of this Disorder,
or attempt to assign any one for it myself, I shall first take notice
of the principal opinions that have been advanc’d to account for it,
and examine how far they are confident with the laws of the animal
œconomy; that the judicious reader may see how necessary further
enquiries into the nature of this Disorder may be.
Doctor Willis says, That the Night-mare is owing to some incongruous
matter which is mix’d with the Nervous Fluid in the Cerebellum[1].
But, as he has not told us what this matter is, or how it is produced,
we can afford it little credit in this enquiry; because plethoric
persons, who abound with the purest and richest Blood, in whom such
incongruous matter is suppos’d least to prevail, are most subject to
this Disorder[2].
Bellini, who, in many other cases, is allow’d to be a pretty accurate
theorist, was strangely mistaken in this, when he said, That the
Night-mare is an imaginary Disease, and proceeds from the idea of some
demon, which existed in the mind the day before[3].
This account is very unworthy a physician, and is a strong evidence
that he never felt the heavy effects of this Disorder; otherwise he
would have allow’d it to be a real Disease of the Body.
A metaphysician has laid great stress on this Disease, as an argument
in defence of some of his wild opinions. He asserts, That it is owing
to the operation of certains demons, which impose on, and torment, the
mind in sleep[4].
This ingenious hint he took from Bellini, who probably stole it from
Paracelsus’s doctrine of Archeus faber[5].
The ingenious Doctor Lower is the first author I met with, who observ’d
the horizontal position of the Body, and assign’d it as a remote cause
of this Disorder, but seems to attribute it immediately to a collection
of Lymph in the fourth Ventricle of the Brain.
He says, “Si supine dormiant, Ventriculus ille quartus, Lympha
nimium distensus, Medullam Oblongatam sua gravitate premit, ideoque
fluxum liquidi Nervosi in Nervis cordi & respirationi inservientibus
impedit[6].”
Perhaps he did not apply his first observation so well as might be
expected from one of his abilities; for it seems needless to wait for
a slow secretion of Lymph to produce this Disease, since, according to
his own account, the return of the Blood from the Head, by the Jugular
Veins, is in some measure prevented, and by that means a greater
quantity of Blood than usual will be collected in all the vessels of
the Brain; which might better answer his purpose, and more effectually
obstruct the nervous influence. But before either of these causes could
be removed by common methods, life would be at an end, and every fit
of the Night-mare would be mortal; but that it often happens otherwise,
many can testify. Doctor Lower seems to have founded this theory on the
dissection of a Man who died of a Hydrocephalus, and not immediately of
the Night-mare: hence that case is ill applied by Bonetus[7].