GENERAL SURVEY AND CONCLUSION 187 



is also shown sometimes after continuous stimulation,, 

 not only in animal tissues, but also in metals (fig. 115). 



Modified response. In the case of nerve we saw 

 that the normal response, which is negative, sometimes 

 becomes reversed in sign, i.e. positive, when the 

 specimen is stale. In retina again the normal positive 

 response is converted into negative under the same 

 conditions. Similarly, we found that a plant when 

 withering often shows a positive instead of the 



Before After Before After 



FIG. 116. MODIFIED ABNORMAL KESPONSE IN (A) NERVE AND (M) METAL 



CONVERTED INTO NORMAL, AFTER CONTINUOUS STIMULATION 



(A) is the record for nerve (recording galvanometer not being dead-beat shows 

 after-oscillation) ; the abnormal ' up ' is converted into normal ' down ' after 

 continuous stimulation. (M) is the record for metal, the abnormal ' down ' 

 being converted into normal ' up ' after like stimulation. 



usual negative response (fig. 28). On nearing the death- 

 point, also by subjection to extremes of temperature, 

 the same reversal of response is occasionally observed 

 in plants. This reversal of response due to peculiar 

 molecular modification was also seen in metals. 



But these modified responses usually become normal 

 when the specimen is subjected to stimulation either 

 strong or long continued (fig. 116). 



