GENERAL PHYSIOLOGY OF NERVE-TISSUE. 125 



2. With an>ascending current of the same strength. After prelimi- 

 nary testing of the excitability and the subsequent closure of 

 the polarizing current, it will be found that stimulation of the 

 extrapolar anodic region will provoke a much less energetic 



^F 



REGION OF 

 ^ INCREASED EXCITABILITY 



SECONDARY COIL 



FIG. 53. DIAGRAM SHOWING THE REGION or INCREASED EXCITABILITY CAUSED BY 

 THE PASSAGE OF A GALVANIC CURRENT, STIMULATION or WHICH GIVES RISE 

 TO INCREASED CONTRACTION. 



contraction or perhaps none at all. Stimulation of the extra- 

 cathodic region, though of increased excitability, as shown by 

 the previous experiment, may also fail to provoke a contraction, 

 owing to the diminished conductivity of the region in the neighbor- 



REGION OF 

 DECREASED EXCITABILITY 



FIG. 54. DIAGRAM SHOWING THE REGION OF DECREASED EXCITABILITY CAUSED 

 BY THE PASSAGE OF A GALVANIC CURRENT, STIMULATION OF WHICH GIVES 

 RISE TO DECREASED CONTRACTION. 



hood of the anode. The impulse on reaching this region is 

 blocked in its passage. A similar if not more marked decrease 



