INFLUENCE OP SLEEP ON TIIE PRODUCTION OF IlEAT.
In the course of the twenty-four hours the body is in two very different and in some sort opposite states — the states of sleeping and watching. These two states are principally contrasted in the energy and weakness of the nervous system: from a perfect consciousness of all that is passing, we suddenly observe a complete suspension of this office in the whole circle of the functions of relation. At the same time the motions of the circulatory and respira tory system become slower. No more is needed to lead to the conclusion that in this state the temperature must be lower ; this is an inference we draw without risk of error. But the degree in which these motions are retarded is ex tremely limited ; and the depression of tem perature must be expected to he in the same proportion : it is in fact very slight, althoush appreciable. What would happen were the retardation in the important motions mentioned more considerable? The temperature would suffer a corresponding and great depression, and various consequences might be conceived as calculated to ensue. If the degree of cold did no injury to the economy, the sleep would last the time required to repair by rest the energy which the nervous system had dissipated or lost by its activity during the period of watching. If, on the contrary, the refrigeration attained a considerable degree, it would by the consequent pain stimulate the nervous system so much as to cause it to wake up to general consciousness; but in case the nervous system were not in a condition to feel this excitement, in other words to re-act and produce waking, it would sink into the state of lethargy.
These divers states which we deduce as pos sibilities, as what might be expected to occur in sleep according to the relations of the func tions, do in fact present themselves frequently in nature. It commonly enough happens that we are aroused from our sleep by a feeling of cold, although the external temperature has not changed. With regard to the lethargic
state, although it certainly occurs but rarely, still it has been acknowledged by the most respectable authorities, and its occasional occur rence seems indubitable. That, however, which is rare as regards man may be common and even usual as animals are concerned.
Phenomena presented by hybrrnating animals with regard to the production of heat.—If during the height of summer and during the state of watching a dormouse or a bat be exa mined as to their temperature, this will be found the same as that of many other warm blooded animals. But if either of these animals be examined whilst asleep at the same season of the year, the temperature will be found to have declined considerably. These changes have been determined by Dr. Marshall Hall, to whom we are indebted for many ob servations of high interest upon the state of the circulation in hybernating animals. The writer also observed the same diversities in the temperature of these animals according to their state of sleep or watching; but he had not published his observations at the time Dr. Hall's paper appeared. I lere, then, we have several species of warm-blooded animals which, during the hottest season of the year, exhibit in the two states of sleep and watching a very marked contrast in regard to the temperature of their body, which is high during the waking period, low during that of sleep, the external temperature having no part in the phenomena. The difference of temperature coincides very evidently with the state of the nervous system— its energy in watching, its enfeeblement in sleep—a state which we have already seen to influence in a very great degree the rapidity of the motions of circulation and respiration, which arc accelerated during the energetic con dition, retarded during the period of inaction. A higher temperature in the one case and a lower temperature in the other are necessary consequences.