770 



HIBERNATION. 



ing the comparative temperature of the animal 

 with that of the atmosphere. The slightest ex- 

 citement induces a degree of respiration, with 

 the consequent evolution of heat. 



The plan which is best adapted to determine 

 this question in regard to the bat, and which I 

 have adopted, together with every attention to 

 preserve the animal quiet and undisturbed, is 

 the following : a box was made of mahogany, 

 with a glass lid, divided horizontally at its mid- 

 dle part, by a fold of strong riband, and of 



Fig. 



such dimensions as just to contain the animal. 

 The bat was placed upon the riband, and in- 

 closed by fixing the lid in its place. Being 

 lethargic, it remained in undisturbed quiet. A 

 thermometer, with a cylindrical bulb, was now 

 passed through an orifice made in the box on a 

 level with the riband, under the epigastrium of 

 the animal, and left in this situation. This 

 arrangement is made obvious by the subjoined 

 wood-cut, (fig. 306,) which also displays the 

 mode of examining the circulation. 



. 306. 



It was only now necessary to make daily ob- 

 servations and comparisons between this ther- 

 mometer and another placed in the adjacent at- 

 mospheric air. The layer of silk, and the por- 

 tion of air underneath, protected the animal 

 from the immediate influence of the tempera- 

 ture of the table, on which the box was placed. 



The following table gives the result of obser- 

 vations made during many days, in very vary- 

 ing temperatures. 



Temperature of Temperature 

 Date. the Atmosphere, of the Animal. 



From this table it is obvious that the tempe- 

 rature of the hibernating animal accurately fol- 

 lows that of the atmosphere. When the changes 

 of temperature in the latter are slight, the two 

 thermometers denote the same temperature. If 

 these changes are greater and more rapid, the 

 temperature of the animal is a little lower or 

 higher, according as the external temperature 

 rises or falls ; a little time being obviously re- 

 quired for the animal to attain that temperature. 



Similar observations were made during the 

 first three days of February. On the 4th, how- 

 ever, the temperature of the atmosphere rose to 

 50J; that of the animal was now 82, and there 

 was considerable restlessness. On the 6th, the 

 temperature of the atmosphere had fallen to 

 474 , and that of the animal to 48, whilst there 

 was a return of the lethargy. 



After this period there were the same equal 

 alterations of temperature in the animal and in 

 the atmosphere, observed in the month of 

 January. 



It is only necessary to add to these observa- 

 tions, that the internal temperature is about 

 three degrees higher than that of the epigas- 

 trium. In two bats, the external temperature 

 of each of which was 36, a fine thermometer, 

 with an extremely minute cylindrical bulb, 

 passed gently into the stomach, rose to 39. 



The following experiments, made by the 

 celebrated Jenner, illustrate this point : 



" In the winter, the atmosphere at 44, the 

 heat of a torpid hedgehog at the pelvis was 45, 

 and at the diaphragm 48i. 



" The atmosphere 26, the heat of a torpid 

 hedgehog, in the cavity of the abdomen, was 

 reduced so low as 30. 



" The same hedgehog was exposed to the 

 cold atmosphere of 26 far two days, and the 

 heat of the rectum was found to be 93 ; the 

 wound in the abdomen being so small that it 

 would not admit the thermometer.* 



* The animal had become lively. See Hunter 

 on the Animal (Economy, p, 113. 



