Liebeault 1 has referred the winter sleep of the dormouse to psychical causes analogous to suggestion, and proved already at that time that cold could not be the cause of this sleep, since the same animals not infrequently slept in summer and in warm rooms, and because a Madagascar mouse regularly falls into lethargy during the warmest time of the year.

I myself have made the following personal observations: 2 In the year 1877 I was in Munich. I was offered two dormice (Myoxys glis), because their owner had been bitten by them. He gave them to me in the winter, and I was astonished to find that they were not asleep, but that they were very lively, which I ascribed to the warmth of the room. I placed them in a wire cage, standing some five to six feet high, in the middle of which was a small fir-tree of the same height. I allowed the little animals to run about in my room besides. They remained lively all through the winter, and ate up a large quantity of walnuts and hazel-nuts. When one of them was gnawing through the nutshell with much difficulty the other came up behind noiselessly, and tried to snatch it away from the first. They remained wild and inclined to bite.

After having eaten a lot during the whole spring, they became very fat, and I was not a little surprised to see them fall into a lethargic sleep one after the other in the month of May. This was contrary to the assertions of the books, which state that the sleep is the result of the winter cold. They had got as fat as little bears, their movements had become slower, and they crept together into a corner and became completely lethargic. Their body temperature sank while they were in this condition, 2 Ford, Revue de l'Hypnotisme, April 1, 1887, p. 318. 309 their respiratory movements became slower, and their lips cyanotic. When put into the open air the animals, which were more or less rolled up, stretched themselves partly when turned on their backs. On pricking them with a needle, they made a reflex movement, and uttered a mild grunt or hiss. I was able to awaken them for an instant by stimulating them strongly, but they relapsed into their lethargy as soon as I left them alone again.

1 Liebeault, "Du Sommeil et des Etats Analogues." (Paris, 1866, Masson.)

I then made the following experiment: I took one of the dormice and placed it on the top branch of the fir-tree. Although it was asleep, to bring the sole of its foot into contact with the thin branch of the tree was sufficient to call forth a reflex flexion, by means of which it clung to the branch with its claws, just as it would have done had the corresponding instinctive movement taken place during the waking condition. I then let the dormouse go, hanging on one branch with one foot. Soon it gradually sank into a deeper sleep again. The muscles of the clinging foot slowly relaxed, the polar or plantar surfaces of the foot extended themselves slowly, and after a short time only the extremity close to the claws held on to the branch. I thought that my dormouse would have fallen. However, as it was beginning to lose its balance, its nervous system was pervaded by a sort of instinctive flash, and the other foot grasped that branch which lay next lowest, so that the animal had thus climbed down one step. The same scene then began again: the dormouse went fast asleep again; the foot relaxed again slowly, until it nearly let go, then the other foot grasped a branch lying a little lower. In this way the animal climbed down the tree from the top to the bottom without awakening or falling until it arrived at the floor of the cage, where it continued to sleep. I repeated the experiment several times with both dormice, always with the same result. Neither of them fell on a single occasion.

The lethargic sleep of my dormice, although interrupted from time to time for a few hours or even a day by more or less complete awakening, during which time they took some food, lasted for the greater part of the summer, and gradually left off in the month of August. The little animals had slept through the great heat of June and July. They were considerably wasted toward the end of their lethargic sleep - still, less than I had expected. During the lethargy their body temperature was about 20° to 22° C, as far as I could measure it. with a very imperfect thermometer.

These facts prove conclusively that the so-called winter Bleep of the dormice does not depend on low temperatures. Perhaps the nutrition, and especially the accumulation of fat in their body tissues, plays a leading part in it. But it seems to me to he probable, from the observations recounted above, that this condition, independent of what cause produces it, is closely related to hypnosis on the one hand and to catalepsy on the other. 1

It is a fact (Liebeault, Bernheim, Wetterstrand) that one can produce a deep, long-lasting catalepsy, with slowing and weakening of all the living functions, in man by means of suggestion under certain circumstances. It is further certain that the dormouse never sleeps, when it is free, outside its nest, that it makes its preparations for the sleep, and that in consequence the setting in of the sleep depends up to a certain degree on association conceptions. My observations prove that even during the lethargic sleep certain purposeful movements can be incited by sensory stimuli. The relatively sudden transition from the waking to the sleeping condition and the reverse, and also the temporary awakening and going to sleep again mentioned above, speaks in favor of the part played by suggestion in the winter sleep of the dormouse. These facts appear to me to prove that the appearance of the lethargy depends on two components: (1) The accumulation of fat, predisposing to somnolence; and (2) the suggestion acting on the nervous centers through associative means.

1 It was only after publication that I become aware of an earlier work of Quincke's ("On the Thermic Regulation in the Marmot. Archiv fur exprri-mentelte Pathologic und Pharmakologie, vol. xv.). The author presumes, on the ground of experiments, another (internal) cause besides cold for the onset and termination of the winter -loop. He writes: "It appears to me as if on awakening (and becoming warm) movements and reactions may take place even during lower temperatures, and on going to sleep (becoming cold) these become sluggish even during higher temperatures. For this reason I think that the alteration of the body temperature only follows the onset and termination of the other symptoms of sleep, and does not produce them. The going to sleep again after spontaneous awakening (in winter, etc.) takes place at very different rates in different individuals. This, too, chows that, although the external conditions - rest and suitable temperature - are necessary conditions for the onset of the winter sleep [this is, as we have seen, an error - Forel], the actual cause for the onset must be another (internal) one." Quincke saw the temperature sink in the marmot down to 7° and even to 6° C. during the winter sleep.