Sleep may not only become imperfect after having been complete, but it may also be so from the commencement, in consequence of unfavourable circumstances. Thus a person may fall asleep on horseback; but some of the muscles continue in action sufficiently to preserve the equilibrium, and even to keep hold of the bridle. I have sat by a coachman who was fast asleep as to his senses, but so far awake as to the motor nerves and muscles, that he remained erect on his box, and did not allow the reins or the whip to fall. It is curious to watch, in such cases, the alternation from sleep to waking; thus by a jolt of the coach the driver would awake for an instant, be aware of his condition, give the whip a languid flourish, and then go off to sleep again.

It is, however, well-known that persons may fall asleep even while in the act of walking. This fact was observed among our soldiers in the forced marches during the retreat upon Corunna. The sleep in such cases is partial.

I should, in connection with this department of my subject, - imperfect sleep, - here speak of double consciousness; but before doing so, I must say a few words about waking.

The process of waking, like that of falling asleep, may be sudden or gradual; the latter is, perhaps, the most natural change. If we watch a person undergoing it, we may observe him first moving bis limbs, then changing his position, then opening his eyes, which however he may close again, and relapse into sleep; then speaking some incoherent matter, as it seems to us, but no doubt rational to him, and conformable to his dream; then he gives a sort of answer to some question we have put, but still wide of the mark; then there is a second opening of the eyes, a stare, a sudden burst of the truth of things, as it seems to us, but to him the exchange of one reality for what was, a moment before, reality to his apprehension, though he now acknowledges that it was all shadowy and fanciful; then he stretches his limbs, that is, puts them from a state of flexion into one of extension, yawns, perhaps, and says he is still weary, and must sleep again:-

"The messenger approaching to him spake;

But his waste words retourned to him in vaine; So sonud he slept that nought monght him awake.

Then redely he him thrust, and pusht with paine, Whereat he 'gan to stretch; but he ageine

Shooke him so hard, that forced Mm to speake. As one then in a dresms, whose dryer brains

Is tost with troubled sights and fancies weake, He mumbled soft, but would not all bis silence breaks." SPENCER, C. 1, 42.

But in other cases the transition from sleep to waking is sudden; it may be so from a strong desire present when asleep to do something important after rising, which recurs to the mind immediately on waking. But cs the transition is quick, merely because the Bleep y light. The individual is sometimes unconscious ig slept; after very deep sleep, for instance, when ims were so feeble as not to be remembered. When slept pretty soundly, he is generally conscious of done so by the great change of the waking sensations. If his sleep has been uneasy and imperfect he often denies that he has slept at all. He has been in a quick alternating succession of sleeping and waking states. The sleeping states have been so mixed up with outward sensations, and the waking states have had so much of drowsiness in them, that when he is fairly awake he entertains a strong impression that he has been awake the whole time. The waking impressions run into each other, and give the idea of uninterrupted continuity. Thus, I remember once sleeping uneasily in the house of a medical friend, whose night-bell rang three times in the course of the night, and in the morning I could hardly be convinced that there had not been an incessant ringing of bells the whole time.

Often we awake, feeling very weary. This may arise from excess of mental action in dreaming, and from unpleasant feelings. But sometimes it is only a residual torpor in the nervo-motor apparatus, which goes off as soon as we are out of bed. At other times, however, it is real languor, dependent on the want of nourishment, and is removed immediately by food. Some persons sleep more in a given time than others; that is, the sleep is more complete, and the refreshment, consequently, more decided.

The mental invigoration is sometimes very remarkable. Difficulties which posed the individual when he fell asleep are now resolved in an instant. In Sir W. Scott's Life it is mentioned, that after composing a great number of verses over night he would sometimes come to a point beyond which he could not advance a step; - a refractory rhyme) an entangled plot, or some other poetic stumbling-block. In such cases he used to give the matter up, confidently expecting that on the following morning he would be able to surmount the obstacle before leaving his couch ; an expectation which was scarcely ever disappointed.

Schoolboys used, in my time (I know not what they do now with modern improvements), to con over their lessons immediately before lying down, and on waking the task would be fresh and clear in their memories. It is surprising-how rapidly one returns after a sleep, though it may have been spent in busiest dreaming, to the train of thought that immediately preceded it. On awaking in the morning we take up the thread of a speculation just as we had left it on the mental distaff, when seduced into weaving thoughts of "such stuff as dreams are made of."

I now return to the consideration of double consciousness. We have seen that the apparatus of speech may awake and act in correspondence with the ideas of the dream only, or with those suggested by sounds, the sense of hearing being also awake; and also that the locomotive apparatus may be in action without the sense of vision, as in the case of the somnambulist who comes in contact with outward objects; or with a complete power of vision. This latter state abuts immediately on the present topic. The person sees, hears, walks, has, in fact, the ordinary attributes of the waking state, and yet is not awake. He may pass from that condition into ordinary slumber, and then wake up like other people; or the transition may be from the morbid condition to the ordinary waking state without intermediate sleep. This is double consciousness.