198 INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



it was reported that the tibial nerves of the albino rat stopped conducting 

 at a temperature 4°-5°C higher than did the ventral caudal nerves from the 

 same animal. No adaptation was noted in the case of the ventral caudal 

 nerve. Perhaps the most interesting study of this series was the one (4) 

 in which a gradient in temperature sensitivity was found for the superficial 

 peroneal nerve of the Herring gull. Not only was the metatarsal portion 

 of this nerve able to conduct at much lower temperatures than the tibial 

 ]iortion, but the metatarsal portion alone was able to adapt to an environ- 

 mental change in temperature. These studies suggest that both adaptive 

 and non-adaptive systems occur in nerve fibers and an analysis of these 

 would appear to offer some hojje of understanding the actions of tempera- 

 ture on nerve cells. 



There are of course a number of observations made in the course of this 

 investigation which are at present impossible to explain. Some of the ef- 

 fects may eventually find explanations in terms of some of the extraneous 

 factors associated with whole nerve preparations. Others, however, may 

 involve factors operating at the level of the excitable membrane. The cause 

 of the differential interference with conduction in the A, B and C groups 

 of fibers by drugs and ions continues to be a problem for which no solution 

 is at hand. The nature of the selective action, in which some C fibers be- 

 have like the A group and other C fibers act with the B group, eliminates 

 such factors as fiber size, surface relation, thickness of myelin, nodes of 

 Ranvier and certain gross anatomical considerations. Then there are the 

 curious observations showing that compounds like choline and TMA are, 

 taken together, neither inert nor are they equivalent in their interactions 

 with sodium. These might be considered as trivial types of responses if it 

 were not for the fact that quaternary ammonium compounds are of physio- 

 logical significance. 



REFERENCES 



1. Bernard, C. G. and R. Granit. Nerve as model temperature end organ. J. Gen. 

 Physiol. 29: 257-265, 1946. 



2. Chatfield, p. 0., A. F. Battista, C. P. Lyman and J. P. Garcia. Effects of cooling 

 on nerve conduction in a hibernator (golden hamster) and non-hibernator (albino 

 rat). Am. J. Physiol. 155: 179-185, 1948. 



3. Ch.'VTFIeld, P. O. and C. P. Lyman. Effects of temperature on the ventral caudal 

 nerve of the rat. Am. J. Physiol. 177 : 183-186, 1954. 



4. Chatfield, P. O., C. P. Lyman and L. Irving. Physiological adaptation to cold of 

 peripheral nerve in the leg of the Herring gull (Lnrns argcntatus). Am. J. Physiol. 

 172: 639-644, 1953. 



5. Crescitelli, F. Some features in responses of different nerve fiber types to a 

 deficiency of sodium. Am. J. Physiol. 169: 1-10, 1952. 



6. Crescitelli, F. Carbamate conduction block in frog nerve fibers. Am. J. Physiol. 

 155: 82-91, 1948. 



