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THE FREEZING OF FROG'S NERVE, WITH SPECIAL REFERENCE 

 TO ITS FATIGABILITY. By John Tait. (From the Laboratory 



of Physiology, Edinburgh University.) 



During the course of an investigation into the influence of low tempera- 

 ture on the conductivity of frog's nerve (1), (2), I often had experiments 

 interrupted by the freezing of the nerve. I used the gastrocnemius nerve- 

 muscle preparation, taking the muscle response as an index of the state of 

 the nerve, of which the middle portion was cooled, while the extreme 

 central and peripheral ei ds, as well as the muscle, were more or less pro- 

 tected by insulation from cold radiation. When freezing occurred the 

 muscle would suddenly begin to twitch, or then pass at once into a condition 

 of prolonged tetanic contraction, followed after a minute or so by irregular 

 convulsive movements. These continued for two or three minutes, the 

 contractions becoming feebler and feebler until they finally ceased. The 

 nerve then refused to conduct. In other cases again, one or two little 

 twitches of the muscle, followed by absence of conductivity, was all that 

 indicated the onset of freezing. In every case after such irregular muscular 

 movements the nerve was found on examination to be hard and stifi", and 

 had a white, opaque appearance as if covered with hoar-frost. 



At first it seemed that the frozen nerve was killed, for no recovery 

 occurred after thawing. Further observation showed that the death of the 

 nerve in such instances was due to mechanical injury during the frozen 

 condition, for, out of curiosity, I had been in the habit of touching the 

 frozen nerve with a pencil to test its rigidity. On ceasing to interfere with 

 it in this way I found that subsequent thawing restored the conductivity. 

 Since then I discovered that Boruttau had previously made similar 

 observations (3). 



The conductivity of the frozen nerve does not, as a rule, come back 

 immediately on thawing. Some time usually elapses before conductivity is 

 restored. In cases of doubt as to the actual vitality of the nerve, I always 

 found that after a rest of an hour or two in Ringer's solution the con- 

 ductivity did return. We may consequently take it that a frozen nerve, 

 while very susceptible to mechanical injury, is not necessarily killed by 

 freezing. 



Such a result is not at all surprising when we consider that poikilo- 

 thermic animals in general may be frozen hard without sacrifice of life. 

 The experiments of Raoul Pictet (4), to whom most of our know- 



