It sometimes appears in very early life, in which case it generally sticks close to the patient, almost all his days. In some, however, such a change in the constitution takes place at puberty as destroys altogether that predisposition to this affection, which existed in early life. Females appear much less subject to it, than males, though by no means exempt. Of these, virgins and pregnant women are more particularly liable to its attacks, as well as all those who are much visited by hysterical affections, constipation, and flatulency. It is sometimes also found to accompany the _chlorosis_ or green sickness. On the whole, however, it is of comparatively rare occurrence amongst females. Neither is this disease very common in advanced life, unless where corpulency, or a tendency to lethargy exists. In those cases however where it does occur, it is more to be dreaded than in youth or middle age. It is no unfrequent attendant on asthmatic persons. The opinions of medical men with respect to the immediate cause of this disease, or what by them is termed its proximate cause, have been various and discordant, as generally happens in all obscure investigations. In all probability every one of them are wrong, so that it can be of little utility to inquire into them. There is however one idea, which seems to be more universally adopted than any other, and which deserves notice; it is, that this affection is produced by a cause purely mechanical, and depending on the position of the body. Some plausible theories have been formed on this supposition, by assigning to the different thoracic and abdominal viscera, certain relative positions which would occasion a temporary pressure upon the organs of respiration, or upon some branch of the intercostal nerves. With respect to this mechanical pressure, arising from any imagined position of the patient, what I have already said on that score, renders this hypothesis vain, for there is no position in which it is possible for a person to fall asleep, in which I have not been attacked by Night-Mare. Neither is there any more dependence to be placed on the generally received opinion, of the disease being induced by a full stomach. It may naturally be supposed, that any person labouring under this affection to the degree which I have stated, although I have as yet given a very feeble idea of its extent, would take every possible precaution to keep clear of the causes, which were so generally believed to have produced it. I religiously abstained, for many years from eating any thing after dinner, and took dinner also at as early an hour as two o’clock. It was during this period that I suffered most from the disease. I think I may safely assert, that for more than twenty years, I have never once, to the best of my recollection, fallen asleep on my back, or ever found myself in that position on waking. When night after night has been rendered miserable by this enemy of repose, I have had recourse to every