HAving now discover’d what appears, to me, to be the immediate cause of the Night-mare, viz. the pressure of the Heart on the left or inferior Auricle and Pulmonary Veins, which stops the motion of the Blood through the Lungs, and occasions a general stagnation; let us examine how that hypothesis will account for the several Phænomena or Symptoms, mention’d formerly in the description of this Disease.
The first Symptoms that occur in that catalogue, are frightful Dreams, which generally are the forerunners of this Disorder. “In hoc genere (Somniorum) est Εφιαλτης quem publica persuasio quiescentes opinatur invadere, ac sentientes pondere suo gravare12.”
I shall not here undertake to solve that Phænomenon, which has so long puzzled the Metaphysicians, nor pretend to account for all kinds of dreams in a mechanical manner.
However, every one knows that the harmony and connection between the Body and the Mind are so establish’d and constituted, while they are united, that the Diseases of the one always affect the other in a very sensible manner; and experience daily demonstrates, that violent passions of the mind produce Fevers, Fainting Fits, and other severe effects on the Body; e. contra, violent shocks of the Body, acute Diseases, &c. frequently disturb, and raise strange commotions in the Mind, or at least excite extravagant, wild ideas in it. Accordingly we find, that the most eminent Physicians have not scrupl’d to assert, that these effects are often owing to Obstructions and Inflammations of the Membranes of the Brain. If so, may not the violent distentions of the Vessels of the Brain (which always precedes and attends a fit of the Night-mare) make such strong impressions on the origin of the Nerves, or Sensorium Commune, as to occasion hideous associations of ideas, and form frightful spectres in the imagination? Are not these monstrous dreams intended as a stimulus to rouse the sentient principle in us, that we might alter the position of the Body, and by that means avoid the approaching danger? Is not the horizontal posture of the Body, which produces a Plethora in the Vessels of the Brain, and many odd sensations, the most general cause of dreams? Do they ever dream, who sleep in an erect position? Are not the luxurious and the plethoric most subject to disagreeable dreams? Is not the motion and titillation of the Animalculæ in Semine Masculino, the cause of the agreeable dreams which attend nocturnal emissions? Have females such emissions in sleep? Does not perfect sleep consist in a total suspension of the operations of the Mind? May not dreaming, in general, be consider’d as a Disorder of the Body, and justly attributed to some cause, which stimulates the Sensorium Commune, and prevents perfect rest? Do people that sleep after much fatigue, ever dream?
The vast oppression on the Breast, and immobility of the Body, which are always felt in this Disorder, probably arise from the quantity of Blood collected in the Lungs, Vena Cava, right Ventricle, and Auricle of the Heart; nor does the Mind appear to be mistaken in this case, as some have imagined; for it seems the same with regard to the Mind, whether the real action of the Muscles be constrain’d by a superior external force, or the influence of it over these Muscles be hinder’d by an internal cause. In a fit of the Night-mare, the Mind, conscious of the dangerous situation of the Body, in vain endeavours to alter it, because its power over the Voluntary Muscles is some way suspended, by the obstruction of the Blood; yet the Mind may exert itself as much as if it strove to remove the greatest obstacle. In this case the Mind generally ascribes the immobility of the Body to some great weight laid on the Breast; whereas the cause is really internal: and people judge of the greatness of the oppression, according to the efforts nature makes to overcome the obstruction of the Blood in the Lungs.
Besides, in heavy or profound sleep, the voluntary motions are generally stop’d. Hence, when people awake suddenly, they are for some time Paralytic, before the Animal Spirits obey the commands of the Mind, and actuate the Muscles in the usual manner.
The indistinct Voice is probably owing to the same cause; for the Muscles of the Tongue and Larynx, which form distinct sounds, are of the vo luntary class, which, as was said before, are generally suspended in sleep.
The collapsing of the Lungs, which are, at this time, overloaded with Blood, will exclude the air, that necessary medium of sounds, and sole vehicle of voice.
Heavy sighs and groans are the emphatic expressions of nature in distress, and generally arise from some obstruction in the Lungs; but in a fit of the Night-mare there appears a great accumulation of Blood in the vessels of that part, whence these Symptoms are easily accounted for. It may be observ’d of sighing in general, that when the attention of the Mind is deeply engag’d to any particular object or sensation, and either neglects or is restrain’d from exerting its influence over the organs of respiration, the Blood is stop’d in the Lungs, so that it becomes necessary to draw in a large Chestful of air, in order to give the Blood a free passage from the right Ventricle of the Heart to the left. Hence Melancholy persons, profound Mathematicians, and fond pining Lovers, are most subject to that affection. Such people are also very liable to many Hypochondriac and Chronic Diseases; which often proceed from a defective respiration, or a too slow motion of the Blood through those parts which are agitated by the alternate dilatation and contraction of the Thorax. Hence the Liver and Spleen and the Lungs themselves must suffer most when the attention of the Mind is engag’d by some Disease of its own, and it becomes less sensible of the Disorders of the Body. Hence people in Grief, &c. labour under a double Disease, which, on account of the anxiety, weight, and oppression that is felt from the Blood stagnating about the Heart, is commonly termed Heart-breaking.
An Uneasiness or Anxiety, and Palpitation of the Heart, are the last Symptoms that are commonly felt of the Night-mare, which proceed from the cause lately mention’d; as ’tis then necessary that the Heart should contract itself more frequently, in order to discharge the Blood collected in the Vena Cava, the right Sinus Venosus, and Auricle, during the fit.
Having done what I propos’d in this Chapter, and given the best account that I know of the Symptoms, I should now proceed to the Prognostics and method of Cure; but, as I have shewn how the vital motions are stop’d, and a general stagnation of the Blood is produc’d, it is also incumbent on me to explain how the motion of that vital stream is renew’d by the efforts of nature alone; otherwise it might be objected, that, according to my theory, unless where art interpos’d, every fit of the Night-mare would be mortal.