On Hybernation. 
_Ithas been observed that animals which do not hyber- 
ess a temperature considerably higher than the 
po ti they: inhabit, while those that do, are but a few 
degrees more elevated than their surrounding medium. 
Sir John Hunter, in his experiment on the power of ani- 
mals producing heat, had frequent occasion to place fish in 
a reduced te mperature, and uniformly found that when the 
of his experiment was no longer able to generate 
heat sufficient to resist the effects of cold, the va frozen 
could not be completely recovered. In all his experi- 
ments upon the freezing of animals, he was unable to re- 
store er actions of life by thawing, from which the con- 
clusion may be drawn that circulation once completely 
stopped, can never be recovered. An earth-worm frozen 
Tae nese time was completely dead when thawed.* 
The moulting of birds as well as their migration is a 
species of hybernation. The first is a preparation for 
hone and their change of colour, adapting itself to the 
eason, y poner the cenieeegny: and causes 
f seasons produces its influence on the 
he shee of Africa almost without fur, and in Scotland the 
veal is pulled from the sheep when ready to fall off. 
same cause, perhaps, produces its effects more pow- 
‘fully on animals than on birds. e ermine, whose 
fi ris so Phe ga undergoes four chang 
— g the summer months its iach is wal a pale reddish 
3 in harvest it becomes clouded with pale 
_ Its winter dress furnishes the valu- 
Rade iB 5 pring: it becomes 
in the month of May it complete- 
ain fear Vol. X. part 
on of birds has been noticed by our earliest 
their wonderful precision and order have 
wareans source of delight to the observation of the 
student of nature. Their periods and habitation so well 
* Animal Eronomy, pp. 109, 112. 
eS ae 
sshutrueranencsts crepes eae 
