INFLUENCE OF EXTREME HEAT AND COLD. 



Numerous observations show that the temperature of animals living 

 in the Arctic regions is equal to that of animals of the same classes in 

 temperate climates. The following are some of the results obtained by 

 different explorers : 



The limits of extreme cold are generally reached when the water in 

 which the animals live, or the lymph of their tissues, is frozen. Fishes 

 live in salt water when the temperature is below zero, but usually die 

 when the water is frozen. 



Boyle 3 exposed lampreys in a vessel of water to an exceedingly 

 sharp frost, and found next day that one lamprey was frozen in the ice ; 

 when the ice was partly broken and partly thawed the animal was at first 

 motionless, but in a few minutes recovered, and dragged after it a large 

 piece of ice in which its tail was fixed. Similar experiments were made 

 with similar results upon gudgeons and frogs. Hunter 4 found by 

 experiment that the internal temperature of a frog and an eel could be 

 reduced to -0'6, and that, although the animals appeared to be dead, 

 they revived when the temperature rose. Eegnard 5 found that carp 

 will live in water containing 2J per cent, of magnesium sulphate, 

 even when the temperature is a degree or two below zero ; at 2 the fish 

 appear to be asleep, and at -3 their vitality is so greatly reduced that 

 they seem to be dead, but revive when the water is gradually warmed. 

 Pictet 6 exhibited at one of his lectures frozen gold fish, pike, and 

 frogs, and at the next lecture the same animals alive and well after 

 gradual thawing. According to this observer, fishes can be rapidly 

 frozen so hard that they can be snapped in two, and yet other fishes 

 frozen equally hard recover when slowly thawed. It has been observed 

 by Marcet 6 that gold fish completely embedded in the ice showed no 

 signs of life on thawing, but one fish, which was partly encased in ice 

 and was surrounded by .a little water, appeared lifeless, but recovered 

 perfectly in a short time. Observations and experiments made by 



1 Parry, "Journal of a Second Voyage for the Discovery of a North-West Passage," 

 London, 1824, p. 157 ; Ann. de chim. et phys., Paris, 1825, Ser. 2, tome xxviii. p. 223. 

 - Compt. rend. Acad. d. sc., Paris, 1836, tome ii. p. 621. 

 "Philosophical Works," Shaw's edition, vol. i. p. 688. 



4 "Works," Palmer's edition, London, 1837, vol. iv. p. 131 et seq. 



5 Compt. rend. Soc. de bioL, Paris, 1895, p. 652. 



"Quoted from Marcet, Croonian Lectures, Brit. Med. Journ., London, 1895, vol. i. 

 p. 1367. 



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