89 



to within |°. The fishes were put either directly into the 

 aluminum ice trays lined with cellophane to prevent ad- 

 hesion durino- freezing, or into a paraffined card-board 

 box. The ])ody temi)erature of the experimental animal 

 was ascertained by means of a needle thermocouple in- 

 serted into the muscles of the back of the fish behind the 

 dorsal fin. The various species were found to differ in 

 frost resistance; huUhead, 6 to 7 inches long, recovered 

 after f hour at a chamber temperature of - 18°, while 

 killifish, 4 to 6 inches long, survived 1 hour at -14° to 

 - 15°, these being the hardiest of the species used. In 

 general, the larger fishes of a species supported freezing 

 more easily than the smaller ones. Moreover, a rapid 

 freezing at a somewhat lower temperature proved less 

 fatal than a prolonged freezing at a higher temperature ; 

 thus, fishes frozen for 5 to | hour at - 14° to - 15° recov- 

 ered in most cases, while those frozen for f to 1 hour at 

 - 10° to - 12° generally did not revive. None of the fishes 

 could withstand a temperature below - 18° for more than 

 25 to 30 minutes. Death occurred when the body tem- 

 perature of the fishes dropped below -0.6° to -1° which 

 required 25 to 45 or more minutes depending on the tem- 

 perature of the chamber and the size of the fish. The 

 author concludes that the death point probably lies near 

 the point at which the body fluids freeze. In a few rare 

 cases, fishes with muscles, blood vessels and intestine 

 frozen hard, but with the heart not yet frozen throughout, 

 recovered wdien thawed. It is thought that only when the 

 heart is hard frozen and kept so for some time, does the 

 fish die. The author distinguishes between fishes that are 

 ' * soft frozen, ' ' that is, stiff and apparently dead, but with 

 the body fluids still liquid as is evidenced by the bleeding 

 when they are dissected, and fishes that are ''hard frozen," 

 that is, "frozen through as hard as stone." The former 

 recover rapidly and evince no ill effects of the frost, while 

 the latter, in most instances, do not regain their vitality, 

 or, if they should perchance survive, exhibit marked 

 injuries. 



