bed-clothes off my breast, and by that means gained relief, and not unfrequently, that I had risen from bed, and opened the window to admit air; yet both these ideas have been proved to be incorrect. I have often felt very certain that my right arm was out of bed, and that I had moved it about; but on waking thoroughly, I have found it under the bed-clothes, and in a situation in which it could not have been moved. I cannot help thinking then, that the universal idea of its attacking persons exclusively lying on the back, is founded on an error, arising out of the ordinary sensations of the patients themselves, who have always that idea, let them be in what position they will. Several persons, subject to habitual Night-Mare, have become convinced of the truth of this observation, which I had made to them, after attending more closely to their real situation during the continuance of, and immediately after the paroxysm. I have also convinced one or two medical friends, who were extremely sceptical on that point, that it would attack me in any position, by going to sleep before them, on a chair, or sofa, when my own feelings have indicated the certainty of attack, if I should indulge for a few moments the propensity I felt to sleep. Neither is it necessary for the stomach to be filled with food, in order to produce Night-Mare, as is evident from what I have stated above with respect to the abstinence I observed during the period in which I suffered most from this affection. Experience has taught me that I may eat heartily of some kinds of food, just before going to bed, with impunity; whilst the smallest quantity of some other will inevitably bring on the disease, in spite of all the precautions that can be taken. Thus then we must give up every explanation of the phenomena which occur in this disease, founded upon principles purely mechanical, however plausible they may appear. Neither is the opinion of Darwin more correct, that the Night-Mare is nothing more than a consciousness of the suspension of the power of volition, and a desire to recover that power. If so, it would differ little from sleep itself; or, however fatiguing it might be to the mind, it could not occasion any derangement in the functions. The breathing and the circulation would go on without any interruption, as in sleep; nor would there be any thing that could produce the sense of oppression on the breast. Darwin was well aware of this difficulty, and therefore chose rather to contradict the generally received opinion of oppression and difficulty of respiration. There is no doubt whatever of the difficulty of breathing, which any one may assure himself of, if he could have the opportunity of seeing a patient during the paroxysm of Night-Mare. I have taken considerable pains to assure myself of this circumstance from the evidence of other persons.