696 HYBERNATION. 



plants periodically fold and open : if excluded from light by day, and exposed 

 to strong lamp-light by night, the periods of sleep become irregular at first, but 

 generally, at length, the leaves close by day and open at night. The alternate 

 opening and closing of flowers is analogous, but take place at different periods 

 in different species, and not at the same period with the same changes in the 

 leaves. An acacia has closed its leaves and expanded its flowers at sunset, and 

 expanded its leaves and closed its flowers at sunrise. (Prof. Henslow's Prin- 

 ciples of Descriptive and Physiological Botany, in Lardner's Cyclopaedia, p. 17 1 . sq. ) 

 The functions of plants are very periodical : leafing and flowering occur at 

 certain periods. The regular return of the seasons influences their periodicity, 

 but there is a natural independent tendency to it which, though assisted by the 

 vicissitudes of the season, causes the changes of individuals to be considerably 

 accelerated or retarded. (Prof. Henslow, 1. c. p. 149. sq.) 



The phenomena of hybernating animals, which grow dull on the approach of 

 winter, and at length fall asleep, continuing so till the return of mild weather, 

 and generally endeavouring to be as little exposed to noise, motion, and all causes 

 of excitement, and to lose as little heat during the approaching cold as possible, 

 by coiling themselves up and getting into holes and warm situations, covering 

 themselves with leaves, &c. (and all the classes of animals, except birds, contain 

 species that have the faculty of living in this state), are precisely analogous, 

 though very different in degree, to those of common sleep. The sensibility and 

 all the functions are lessened, the temperature becomes nearly as low that of the 

 surrounding medium, the circulation slow, respiration almost or quite impercep- 

 tible, and digestion suspended. Although all activity is thus reduced in the 

 hybernating state, vitality becomes more tenacious, is less easily extinguished. 

 Mangili cut off the head and neck of a marmot in the state of hybernation in 

 March, and put it in spirits, yet movements were evident in it at the end of half 

 an hour, and galvanism produced strong contractions in pieces of voluntary 

 muscles three hours after they had been cut off ; and even four elapsed before 

 their excitability was much diminished : the heart beat for three hours after de- 

 capitation. He made the same examination in June with a marmot which had 

 been out of hybernation two months ; the muscles showed little excitability 

 under galvanism at the end of two hours, and the heart ceased to beat in fifty 

 minutes after decapitation. (Annales de Museum, t. x. p. 453. sqq.) This is 

 what we should have expected. The augmented tenacity of life, which allows 

 food, air, and heat to be dispensed with in whole or in part, is likely to pervade 

 the muscles and indeed every part of the frame; just as the necessity for air, 

 food, and heat is in all other cases proportionate to the want of tenacity of 

 excitability in muscles and of all vital properties. The sensibility is not so dimi- 

 nished but that " the slightest touch applied to one of the spines of the hedge- 

 hog immediately roused it to draw a deep and sonorous inspiration ; the merest 

 shake" induces a few respirations in the bat. (Dr. Marshall Hall, Phil. 

 Trans. 1832.*) 



* This gentleman endeavours to show that an inverse ratio prevails between 

 respiration and irritability, in which word he includes both tenacity and sus- 



