1903.] 



in the Nerves of Warm-blooded Animals. 



281 



531 



49" 



the lowest point before extinction of the negative variation took place, 

 and both the frog and hedgehog agree in giving a measurable response 

 below 0°. In experiment B on the frog the negative variation 

 reached a maximum at +3 3, 8 C. In the experiment C df on the 

 hedgehog an exactly similar maximum was observed at + 7°"9 C, and 

 plotting out the " cooling " and " warming " 

 curves the latter gave also a maximum at 

 the same point (fig. 7). 



No such maximum was certainly observed 

 in the mammal or pigeon. There were 

 traces of a maximum at 25° C. in the 

 former (in experiment B llb and an earlier 

 experiment on the kitten not recorded 

 above), but the experiments C dg , C dh , C ed , 

 C eh showed no sign of this. Several explana- 

 tions are possible, but it seems preferable to 

 await the result of further experiments 

 before insisting too strongly on any of them. 

 One, however, seems well established, that 

 the negative variation follows the tempera- 



55 



5ti 



46 



40 



35 



ture with a certain " lag." This is seen to 

 a small extent in the nerve of the hedgehog 

 (fig- 7). 



in the rabbit and bird it is larger 

 in amount, and tends to obscure curves taken 

 in this way. 



I have not yet determined the permanent 

 extinction point, recovery took place in 

 experiment B p in the frog after a tempera- 

 ture of - 3° -5 C. had been reached, and in 

 Experiment B ub on the rabbit ( - 2°'5), expe- 

 riments are in progress in this direction. 



The range of temperature through which 

 the nerve can function is obtained by com- 

 bining the figures here observed with those 

 of the former series, and it is found that this 

 range is the same for all the nerves examined, 

 45 -5 for the frog, 45° "2 for the rabbit, and 

 46° "1 for the pigeon, one step higher in the 

 temperature scale in each case (Fig. 8). 



Conclusion. 



(1.) It is possible to examine isolated 

 mammalian and avian nerves under the same 

 conditions as frog's nerves. 



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