own gravity; yet persons who have undergone great fatigue may be overcome with sleep in the act of walking, as once occurred to myself, and which frequently happens to soldiers on a march; this, however, can scarcely be considered as perfect, but only partial sleep, to which may be referred all the peculiarites which distinguish somnambulism. Since sleep is a state of repose, the position which requires the exertion of the smallest number of muscles, is most favourable to its approach. No posture is attended with a more general relaxation of the muscles than that on the back, which is generally preferred, especially by those who have undergone great fatigue. Habit, however, has great influence on the position; to some it appears a matter of indifference, as they can sleep with almost equal facility in any; others can scarcely sleep at all, except in that to which they have been accustomed, and it requires a considerable time before they are reconciled to a change. No position seems to possess any peculiar advantage, except in states of disease, and individual cases, and the original choice is generally directed by mere accident. There are persons who are unable to sleep upon their backs, or if they do so, are almost invariably awakened by an attack of incubus, especially if they have partaken of any solid food previously to retiring. This may arise from the pressure of the stomach upon the descending aorta, by which a greater quantity of blood than usual is sent to the brain : or the distended state of the stomach, by food or flatus, may prevent the proper descent of the diaphragm, and thus create a congestion about the heart and lungs, which is still more likely to take place where any organic disease exists at the same time. Many persons prefer lying on their right side, which position is supposed to favour the descent of the food from the stomach into the duodenum, as well as to prevent the pressure of the liver on the stomach. According to Pliny, " Somnus magis accidit quando parte corporis dextra cubamus.” Physicians in former times used to recommend persons, in their first sleep, to lie upon their right ear; when they awoke, and wished to sleep again, on the left; but when they wished for light slumbers, and to awake with facility, to lie upon neither ear. To be able to sleep equally upon either ear, was supposed to be the sign of an easy and contented mind. Thus, Terence says, "In aurem utramve otiosè ut dormias ; "* and Pliny, in the same sense, "Nihil est quod in dextram aurem fiduciâ mei dormias." Those who labour under a diseased state of the liver generally sleep on the right side, and experience considerable uneasiness if they attempt to lie upon the left, which arises from the pressure of the enlarged or hardened liver upon other organs, or from its increased weight stretching its own ligaments, which are also frequently in an inflamed or morbid condition. Whatever posture we may assume at the commencement of our customary sleep, we seldom continue for any length of time without changing it unconsciously, which is owing to uneasy sensations * Heautonton, Act. 2, Scen. 3. in particular muscles, which cause a sufficient stimulus to excite the action of the muscles, though not to our consciousness of it. It would be impossible to give any precise rules for the regulation of positions, which must be left to the habits and peculiarities of individuals; there is, however, one general rule applicable in all cases, which is, that the head should be elevated in some degree above the level of the shoulders, though not so much as to create any uneasy sensation in the muscles of the neck; and the bed should be so contrived as to make a slight and gradual slope from the head to the feet. As the length to which the present communication has extended will occupy as much space as may be desirable, in the forthcoming part of our Transactions, I shall not, at present, pursue farther my investigations into the nature of sleep; to which subject my attention was some time ago accidentally directed. In every stage of my inquiries I found it involved in greater obscurity; enveloped in a cloud of unsatisfactory theories, as contradictory as unlimited; and even by the most modern and acute Physiologists, very vaguely and imperfectly understood, and given up, as it were, by general consent, as a matter too profound for the reach of human intellect. Though I trust I am equally far from entertaining the presumption that I am capable of adding any thing very material to so difficult a subject, as I am from that despair which would check all investiga tion, from the idea of its futility; it appears to me, that though it may be a laborious, yet it will not be an uninteresting occupation, on a subject which so intimately concerns every one, to present to the members of the Provincial Medical and Surgical Association, some of the imperfect fruits of my researches and reflections. CASE OF ANEURISM OF THE BASILAR ARTERY, SUDDENLY GIVING WAY, AND OCCASIONING DEATH BY PRESSURE ON THE MEDULLA OBLONGATA. BY EGERTON A. JENNINGS, F. L. S. WITH A PLATE. If it be desirable to inflict injuries on living animals to illustrate the functions of different portions of the nervous system, and if such compound injuries can afford data on which to reason, it must be doubly desirable to record those facts which disease presents to our observation, and doubly valuable must be those cases in which the desired injuries exist without the addition of external violence. In the following case a sudden injury was inflicted on the medulla oblongata. The symptoms were so characteristic, and, at the same time, so peculiar, that I have thought the case might not be uninteresting to the members of this society. John Beard, æt. 54, a stout healthy man, had served seventeen years in the army, which he had left about twelve months. He had enjoyed good health until within the last few months, during which |