PREFATORY. IN the following pages I have tried to embody the leading facts about sleep, with such reflections and suggestions as have occurred to me in the course of investigations relating to that rhythmical function of life. I venture to hope they will be of value to the ordinarily intelligent reader, and not wholly unworthy of the attention of the student and practitioner who are concerned, the one to comprehend, the other to relieve, the troubles which so commonly arise in connection with this state of the organismmental and physical. I have aimed at nothing beyond a simple statement of the conclusions at which I have myself arrived. JUNE, 1879. J. M. G. SLEEP. ALL that is certainly known about sleep as a state, or function, of the organism, may be told in a few sentences. The information recently acquired is chiefly negative. Sleep is not, as was once supposed, a condition of the brain and sense-organs, in which activity has been suspended by the pressure produced by congestion; that is too much blood in the vessels-arteries or 'veins-of the cranium. Nor is it, as contemporary physiologists and experimenters have thought and taught, an arrest of activity by diminished supply, or too little blood circulating in the vessels, of the brain. Neither is the phenomenon of natural sleep produced by any chemical or chemico-physical change in the blood itself, which might be supposed to impede or impair the cerebral functions. What is called "determination of blood to the head" may occasion " "heaviness' or "stupor," but it will be of the sort which tends to apoplexy, not to sleep. When sleep follows a drunken bout, or B a blow on the head, or seems to be produced by "compressing the vessels of the neck," the immediate condition set up is morbid. The sleep that sometimes occurs later on in this experiment is reactionary, and intended by nature to be restorative. Again, if the brain and cerebral centres are deprived of their blood-supply by failure of the heart's action, as in faintness, or by loss of blood from any cause, there will be yawning and sleepiness; but the state induced is not sleep. It is one of exhaustion tending towards syncope and death. If the blood be poisoned with carbonic acid, or if it be insufficiently supplied with oxygen-for example, from repeatedly breathing the same atmosphere in a close or crowded room, or from some defect in the number or efficiency of the oxygen-carriers, the red corpuscles of the blood, as when these are affected, perhaps shrivelled and contracted, by the presence of certain chemical properties in the blood, or during the administration of chloroform, or after taking chloral-insensibility may supervene, but not sleep; and if sleep follows, it is easy to recognise the difference of the two states. That such changes in the blood pressure 1 Dr. Fleming, in a Paper in the British and Foreign Med. Chirurg. Review, 1855, Vol. I., p. 529. |