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 gravare[12].”
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?