It appears evident, from the mode of treatment to which this disease gives way, that the primary cause, in whatever manner it may act, has its seat in the digestive organs; nor can any difference, or even error, in explaining its _modus agendi_, in any manner invalidate this doctrine. The ancient physicians seem tolerably well to agree on this point, and consider Night-Mare as a species of epilepsy, arising from a superabundance of _acid humor_ in the _primæ viæ_, and their treatment was entirely directed to the evacuation and correction of that humor. If they were mistaken in their pathological ideas of this affection, they were at all events successful in their treatment; and it was usually their practice to reason from the cure to the cause of a disease, a safe mode of reasoning in medicine. Experience had taught them that a long train of diseases originated from this cause, and a little observation will suffice to convince any man, unprejudiced by medical theories, that Night-Mare originates from no other cause than a defect in the digestive process, whereby the food, which should be converted into good chyle, is transformed into a half-digested mass of acid matter, which is productive of heart-burn, acid eructations, flatulence, and intolerable gripings, with the whole train of dyspeptic and hypochondriacal symptoms. There are many stomachs which convert every thing they receive instantly into an acid, and such will be generally found to be the case with persons subject to habitual Night-Mare, or frightful dreams, and disturbed sleep. Such stomachs too are frequently distended with some acid gas, and I have often found the paroxysm of Night-Mare to be the consequence of this distension alone, and to be immediately removed by any thing which would dispel the gas, such as a glass of peppermint cordial, or gin, or any carminative medicine. A medical gentleman in Norfolk, who laboured under an inveterate disease of the digestive organs for several years, which in the end proved fatal, was dreadfully tormented by the most pertinacious paroxysms of Night-Mare, which threatened suffocation, had recourse to a solution of Ammonia in warm water, which he always drank when the paroxysms of Night-Mare began to disturb him; for whenever they did begin, they always continued to torment him, every time he fell asleep. The success of this plan very far exceeded his expectations. The immediate effect of the medicine was to send up a great quantity of wind from the stomach, which was succeeded by a profuse perspiration, and tranquil, undisturbed sleep. I have always found, in my own case, that Night-Mare was accompanied with distension of the stomach and bowels by flatus, constipation, and acid eructations.