400 



HYBERNATION. 



Animals 

 which 

 become 

 Torpid. 



Edicts of 

 cold. 



We cannot refrain from observing, that these general 

 views do not appear to be the result of a patient inves- 

 tigation of a number of different kinds of torpid ani- 

 mals, but a premature attempt to theorise from a few 

 insulated particulars. Passing, therefore, from these 

 attempts of the anatomist to illustrate the phenomena 

 in question, let us attend to those other causes which 

 are concerned in the production of torpidity. 



From the consideration, that this state of torpidity 

 commences with the cold of winter, and terminates 

 with the heat of spring, naturalists in general have 

 been disposed to consider a reduced temperature as one 

 of the principal causes of this lethargy. Nor are cir- 

 cumstances wanting to give ample support to the con- 

 clusion. 



When the temperature of the atmosphere is reduced, 

 as we have already seen, below 50, and towards the 

 freezing point, these animals occupy their torpid posi- 

 tion, and by degrees, relapse into their winter slumbers. 

 When in this situation, an increase of temperature, the 

 action of the sun, or a fire, rouse them to their former 

 activity. This experiment may be repeated several 

 times, and with the same result, and demonstrates the 

 great share which a diminished temperature has in the 

 production of torpidity. If marmots are frequently 

 disturbed in this manner during their lethargy, they 

 die violently agitated, and a hemorrhage takes place 

 frovn the mouth and nostrils. 



The circumstance of torpid animals being chiefly 

 found in the colder regions, is another proof that a di- 

 minished temperature promotes torpidity. And, in 

 confirmation of this, Dr Barton informs us that, in the 

 United States of America, many species of animals 

 which become torpid in Pennsylvania, and other more 

 northern parts of the country, do not become torpid in 

 the Carolinas, and other southern parts of the conti- 

 nent. 



But while a certain degree of cold is productive of 

 this lethargy, a greater reduction of temperature pro- 

 duces reviviscence as speedily as an increase of heat. 

 Mangili placed a torpid marmot which had been kept 

 in a temperature of 45, in a jar surrounded with ice 

 and muriate of lime, so that the thermometer sunk to 

 16. In about half an hour a quickened respiration in- 

 dicated returning animation. In sixteen hours it was 

 completely revived. It was trembling with cold, and 

 made many efforts to escape. He also placed a torpid 

 bat under a bell glass, where the temperature was 29, 

 and where it had free air. Respiration soon became 

 painful, and it attempted to escape. It then folded its 

 wings, and its head shook with convulsive tremblings. 

 In an hour no other motions were perceptible than those 

 of respiration, which increased in strength and fre- 

 quency until the fifth hour. From this period, the 

 signs of respiration became less distinct; and, by the 

 sixth hour, the animal was found dead. He also ex- 

 posed a torpid dormouse (from a temperature of 41) 

 to a cold of 27 produced by a freezing mixture. Re- 

 spiration increased from ten to thirty-two times in a 

 minute, and without any intervals of repose. There 

 were no symptoms of uneasiness, and the respirations 

 seemed like those in natural sleep. As the tempera- 

 ture rose, respiration became slower. He then placed 

 it in the sun, when it awoke. Two hours afterwards, 

 having exposed it to the wind, respiration became fre- 

 quent and painful ; it turned its back to the current 

 without, however, becoming torpid. 



That cold is calculated to produce effects similar to 

 torpidity on man himself, is generally known. When 



persons in health are immersed in Salt water at the tem 

 perature of 40, the thermometer under the tongue 

 sinks from seven to nine degrees below the standard 

 heat. In a little, however, it recovers its ordinary ele- v 

 vation, and becomes stationary. Exposure to cold has 

 also the effect of diminishing the force of the pulse 

 very much of producing great exhaustion, and an ac- 

 cumulation of blood in the extreme vessels. 



But the effects of a reduced temperature on the hu- 

 man system are still better illustrated in the tendency 

 to sleep, produced by a cold atmosphere in certain si- 

 tuations. Those who have ascended to the summits of 

 high mountains, have, by the exposure to cold, felt an 

 almost irresistible propensity to lie down and sleep. 

 Dr Solander, while exploring Terra del Fuego, though 

 perfectly aware of the inevitable destruction attending 

 the giving way to this inclination ; nay, though he had 

 even cautioned his companions against indulging it, 

 could not himself overcome the desire. When this 

 feeling is gratified, sleep succeeds, the body becomes 

 benumbed, and death speedily arrives. How long 

 this sleep might continue without ending in death, 

 were the body defended from the increasing cold and 

 the action of the air, will probably never be determi- 

 ned by satisfactory experiments. Partial torpor has 

 often been experienced in the hands and feet, which is 

 easily removed by a gradual increase of temperature. 

 We may add, that in the case of persons exposed to 

 great cold in elevated situations on mountains or in bal- 

 loons, there are other causes in operation which may 

 have a tendency to produce sleep. The previous exer- 

 tions have reduced the body to a very exhausted state 

 the pressure of the atmosphere on the body is great- 

 ly diminished, and the air inhaled by the lungs is ra- 

 refied. 



When these torpid animals, kept in a confined state, 

 are regularly supplied with food, and kept in a uni- 

 form temperature, it has been observed that they do 

 not fall into their wonted lethargy, but continue lively 

 and active during the winter season. This experiment 

 has often been repeated with the marmot and other ani- 

 mals. But when in this state they are peculiarly sen- 

 sible to cold. Dr Reeves, in some experiments which 

 he performed, says, " When I was in Switzerland I 

 procured two young marmots in September 1805, and 

 kept them with the view of determining the question 

 whether their torpidity could be prevented by an abun- 

 dant supply of food and moderate heat. I carried them 

 with me to Vienna, and kept them the whole of the 

 winter 1805-6. The months of October and Novem- 

 ber were very mild. My marmots ate every day tur- 

 nip?, cabbages, and brown bread, and were very active 

 and lively : they were kept in a box filled with hay in 

 a cellar, and afterwards in a room without a fire, and 

 did not shew any symptoms of growing torpid. De- 

 cember the 18th, the weather was cold, and the wind 

 very sharp ; Fahrenheit's thermometer stood at 18 and 

 20. Two hedgehogs died which were kept in the 

 same room with the marmots ; and a hamster died also 

 in a room where a fire was constantly kept, though 

 these animals had plenty of hay and food. The liar- 

 mots became more torpid than I ever saw them before ; 

 yet they continued to come out of their nest, and en- 

 deavoured to escape : the food given them in the even- 

 ing was always consumed by the next morning. In 

 January the weather was unusually mild and warm ; 

 my marmots ate voraciously, and were jumping about 

 in the morning ; but at four o'clock in the afternoon 

 I examined them several times, and found them not 



