ANIMAL HEAT. 



671 



proportion : it is in fact very slight, although 

 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 hybernating 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. Here, 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 are 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. 



These facts are interesting under two points 

 of view. 1st, They show precisely the kind and 

 extent of the influence which the states of 

 watching and sleep exert in general on the 

 production of heat in animal bodies ; 2d, they 

 are remarkable in the particular instances under 

 consideration, in this, that the differences exhi- 

 bited during the two states are extreme. It 

 must be allowed, therefore, that those animals 

 in which they take place must have less 

 energetic nervous systems than other warm- 

 blooded animals. From this tendency in 

 the animal economy, there must also be in 

 different species a diversity rather than an 

 equality in the degree in which the phenomena 

 are exhibited. And this is confirmed by obser- 

 vation. Some cool to a much greater extent 

 than others during their sleep in the summer 

 season. They may be said severally to have 

 just as much nervous energy as is requisite to 

 sustain a high temperature in the summer 

 season during their state of highest activity, 

 i. e. during the period of watching, and no 

 more. When the state of excitement ceases, 

 and the collapse that follows excitement 

 supervenes, the languor manifested is much 

 greater than that of other animals in the 

 same condition, and their temperature sinks 

 in proportion. The energy possessed by hyber- 

 nating animals seems barely sufficient to enable 

 them during the summer season to maintain a 

 temperature of body equal to that of warm-blood- 

 ed animals in general. They subsequently pre- 

 sent another phenomenon with regard to their 

 temperature well worthy of particular attention, 

 although it be no more than a consequence of the 

 first. Since it is a defect of energy in the 

 nervous system during sleep which prevents 

 their maintaining the degree of rapidity in the 

 motions of circulation and respiration so essen- 

 tial in their turn to the maintenance of a tem- 

 perature of the body but little inferior to that 

 pertaining to the state of watching in summer, 

 how are they to preserve their temperature even 

 during the watching state when the summer 

 declines into autumn, and the autumn into 

 winter? 



It is evident that if they follow the general 

 rule their respiratory and circulatory motions 

 will be retarded with the fall of the atmospheric 

 temperature, and this by so much the more as 

 their nervous system shows a less degree of 

 energy. It is even presumable that owing to 

 the decline of atmospheric temperature in 

 autumn, they will exhibit a temperature of 

 body during the period of watching analogous 

 to that which they manifest in the heat of the 

 summer season during sleep. And this is pre- 

 cisely what happens. M. de Saissy paid par- 

 ticular attention to the state of these animals 

 at intervals from the month of August onwards. 

 On the 6th of August, the temperature of the 

 air being at 22 c. (72 F.), a dormouse and a 

 marmot marked 36, 5 (98 F.), and a hedge- 

 hog 34 c. (93, 5 F.) in the axilla. On the 

 23d September, the external temperature being 



