DETECTION OF PHYSIOLOGICAL ANISOTROPY 115 



nate which side of two is the more excitable, so here also the 

 more excitable side is that which, on diffuse stimulation, 

 exhibits galvanometric negativity relatively to the other. 

 From this it becomes possible to determine the relative 

 excitabilities of any anisotropic organ, even though it be 

 non-motile, and therefore incapable of exhibiting any con- 

 spicuous mechanical response. The difficulty of applying 

 equal and quantitative stimulus on two- sides simultaneously 



FIG. 82. Responsive Current in Petiole of Musa from Concave to 

 Convex Side 



First series, normal ; after application of chloroform subsequent 

 depression. 



has now been overcome by vibrational stimulation, and by 

 the perfection of the method of thermal shocks. Thus a 

 definite resultant response has been shown to be determined 

 by the differential excitabilities of two parts of an experi- 

 mental tissue. And that from this consideration it becomes 

 further possible to resolve many of the remaining anomalies 

 of electrical response will be fully demonstrated in a sub- 

 sequent chapter. 



