87 



As we sliall see, the results of the investigators diverged 

 widely on this very point of revival after hard freezing, 

 nntil good determinations of the body temperature of 

 fishes experimented upon were made. 



Pouchet (1866) exposed to varions low temperatures 

 gold fishes, small s tickle-hacks, and eels contained in 

 tubes full of water, that he immersed in freezing mixtures. 

 He found that the eels were killed in 1 hour at - 14°, the 

 gold fishes in 2 hours at -19°, but that stickle-hacks, 

 the body of which was only half congealed after 2 hours 

 at - 19°, survived. He emphasizes that he never observed 

 the revival of a completely frozen fish, and that when the 

 animals were entirely caught in the ice they were dead. 

 He could observe some revived fishes carrying pieces of 

 ice attached to their body but the latter had been only 

 partially caught in the ice. 



According to Knauthe (1891), fishes of the genera 

 Cyprinns, Carpio, Carassius, Rhodeus and Misgurnus, 

 laid on ice and covered with snow or ice w^ater, can be 

 maintained alive if the surrounding temperature never 

 drops below -4°, and if the animals do not stay in the 

 rigid condition for more than one hour. 



Pictet (1893) says he could revive gold fishes and 

 tenches which had been left for 24 hours in water at 0° 

 and were then cooled slowly to - 8° to - 15°, at which tem- 

 perature they were brittle. He obtained no revival after 

 a cooling to -20°. Pictet 's experiments, which confirmed 

 the popular opinion of the reviviscence of "hard frozen" 

 fishes, have been generally considered as demonstrative 

 by the biologists until more recent determinations have 

 brought into evidence the fact that the body temperature 

 in fishes is often above the bath temperature for a time 

 much longer than it was generally thought. 



The action of cold alone, ^^'ithout congelation, on fishes 

 was investigated by Regnard (1895). Carps, accus- 

 tomed to water containing 2.5% magnesium sulphate, 

 were cooled slowly in this medium. Cooling was achieved 

 by immersing the container in a refrigeration bath. Reg- 



