462 



COMPARATIVE ELECTRO-PHYSIOLOGY 



shocks, after which its responses to individual stimuli of the 

 former intensity were recorded once more. The subsequent 

 responses show, as is seen in the record, an enhancement of 

 amplitude. 



The next series of responses, in fig. 276, exhibits abnormal 

 galvanometric positivity. It may be mentioned here that 



these abnormal responses are 

 not, as supposed by Dr. 

 Waller, exclusively character- 

 istic of the stale condition of 

 the nerve. For employing 

 other and more delicate 

 methods of record I have 

 found even fresh nerves, 

 under certain conditions, to 

 exhibit this effect. Neither 

 is this positive response due 

 in general to any chemical 

 degradation. Instead of this, 

 as we shall see in the present 

 and succeeding chapters, it 

 may be attributed to the 

 run-down of the latent energy 

 of the specimen, a process 

 which becomes accelerated in 

 isolation. When such a de- 

 pressed specimen is supplied 

 again with the requisite 

 energy, it becomes normally, 

 or even supernormally, ex- 

 citable. The first part of the 



following record (fig. 2/6) gives a series of abnormal positive 

 responses obtained from a specimen of frog's nerve, which 

 was in a somewhat sub-tonic condition. After the appli- 

 cation of tetanic thermal shocks it will be noticed that the 

 responses in the second part of the figure have become 

 converted into normal. 



FIG. 275. Enhancement of Amplitude 

 of Response, as After-effect of 

 Thermal Tetanisation, in Frog's 

 Nerve 



The first three responses are normal. 

 Brief thermal tetanisation is here 

 applied, and the responses subse- 

 quently obtained under original 

 stimulation are seen to be en- 

 hanced. 



