HIBERNATION. 



797 



bat and dormouse the rise may be even more rapid, as shown by the following 

 examples : l 



f = 17 when very quiet } 



Bat-Rectal temperature- =34 wh , en ke and Temperature of 



active, niteen air =10 '5. 

 I minutes later I 



C = 13 4 5 when asleep "j 



Dormouse- \ = 86 ' 78 when awake I Temperature of 



and active, one air = 9 *5. 

 I hour later J 



The rapid rise in temperature is accompanied by a marked quickening of 

 the respiration and of the heart-beat, and by active movements of the body. 

 In some cases, especially in the marmot, there is a convulsive shaking of the 

 body. The increase in the muscular activity appears to be the chief cause of 

 the increased production of heat, although Horvath 2 and Dubois 3 do not 

 accept this view. It is to be noted, however, that Horvath draws attention to 

 the increased respiration and heart-beat, and remarks that when once the 

 shivering movements of the marmot have commenced, nothing can prevent 

 the animal from awaking, and its temperature from rising. Dubois considers 

 that the liver plays the most important part, for he finds that extirpation of 

 the ganglia of the solar plexus, or ligature of the portal vein, and of the 

 inferior vena cava just above the liver, prevents the rapid rise of temperature 

 observed in an awakening marmot. An examination, however, of the experi- 

 ments made by Dubois shows that the influence of the nervous system is 

 considerable, for the greater the motor paralysis the smaller was the rise in 

 temperature. 4 Kemoval of the cerebral hemispheres does not prevent hiber- 

 nation or the rise of temperature observed when the animal awakes. The 

 latter phenomenon, however, is abolished by section of the spinal -cord at the 

 level of the fourth cervical vertebra. 



In the case of bats and dormice, Pembrey and Hale White have shown 

 that the sudden rise in temperature, when the animal awakes, is accompanied 

 by a greatly increased discharge of carbon dioxide. 



The causes of hibernation. The cause generally assigned for hibernation 

 is cold, but a more careful consideration of the facts long ago showed 

 that cold could not be the sole cause of the phenomena. Most observers 

 who have worked at the subject of hibernation have found that even 

 severe cold will not cause an active animal to hibernate. Saissy 5 observed 

 that a low temperature alone was ineffectual, but the continued effect of 

 cold, and a limited amount of air for respiration, caused a marmot to pass 

 into a typical hibernating condition even in summer. Mangili 6 found that 

 torpid marmots and bats were awakened by exposure to severe cold, and that 

 confined air would not cause hibernation. Valentin and Horvath 7 have 

 recorded cases of marmots hibernating under normal conditions during 

 summer; the animals were very fat, and the torpid condition was in all 

 respects similar to that in winter. Pallas states that if the hamster be buried 

 four or five feet below ground in a confined space, it begins to hibernate. 8 



Dormice have been kept throughout the winter in a warm room (16), and 

 yet they hibernated, and were not aroused when the external temperature 



1 Pembrey and Hale White, loc. tit. 2 Loc. cit., pp. 170, 175. 



3 Compt. rend. Soc. de UoL, Paris, 1893, pp. 210, 235 ; 1894, pp. 36, 115. 

 * Ibid., 1893, p. 156. 



5 "Recherches expdrimentales anatomiques," etc., 1808. 



6 Arch. f. d. PhysioL, Halle, 1808, Bd. viii. S. 433, 437, 444. 



7 Vtrhandl. d. phys.-med. Gesellsch. in Wilrzburg, 1881, Bd. xv. S. 209. 



8 See also Paul Bert, "Lecons sur la physiol. com p. de la respiration," Paris, 1870, 

 p. 508. 



