EFFECT OF TEMPERATURE ON CONDUCTIVITY 501 



however, the reversal of response showed that the conduc- 

 tivity was now being depressed. And at still higher tem- 

 peratures it was found to undergo a very great depression, 

 as is seen by the abrupt downward movement of the curve. 

 It is thus seen that, by means of the Method of Balance, this 

 very difficult problem of the variation of conductivity under 

 variation of temperature is made^capable of exact study. 



I shall next describe the results of an investigation into 

 the after-effects of stimulus on conductivity and excitability, 



FIG. 309. Photographic Record Showing Effect of Rising Temperature 

 on Conductivity 



Balance obtained at starting at 33 C. Successive responses recorded at 

 each degree C. of rise of temperature. Record shows increasing 

 .conductivity up to 47 C. A depression of conductivity is seen by 

 reversal of curve to set in at 48 C., and this becomes extremely pro- 

 nounced at 50 C. 



a subject of much difficulty and of considerable theoretical 

 importance. It has been found in Animal Physiology 

 that the sciatic nerve of a frog, for instance, is not equally 

 excitable throughout its length. When such a nerve, with 

 its attached terminal muscle, is cut off from the spinal cord, it 

 is seen to be more excitable the further from the muscle is 

 the point on the nerve that is subjected to stimulation. 

 From this fact that excitation increased with the distance of 

 the point excited from the motor organ, Pfltiger was led to 



