THE MOLECULAR RESPONSIVENESS OF MATTER 



by vibrating it as a whole, a resultant response will occur. 

 But by the application of oxalic acid to one contact, a resting 

 or permanent current has been induced in the circuit. The 

 responsive or action current 

 originated under stimulation 

 is now found to flow in a 

 direction opposite to that of 

 this resting current that is 

 to say, it causes a negative 

 variation of it (fig. 11). 

 The method of response 

 by the so-called negative 

 variation, which is generally 

 employed in studying re- 

 sponsive phenomena in 

 animal tissues, is in reality, 



Ewill be seen later, a form 

 this method of relative 

 :pression. 

 Various means have been described, in the course of this 

 ^napter, for the detection and record of that excitatory change 

 which is brought about by the upsetting of molecular equi- 

 librium under stimulus, 

 and the subsequent re- 

 covery. The responsive 

 change may find expres- 



F ' G ' 



? 



ion in different ways. 

 his expression may, 



4 4 t 



^A IU 



FIG. ii. 



for instance, in the case 

 of living tissues, take the 

 form of mechanical con- 

 traction, or of the elec- 

 trical variation of gal- 

 vanometric negativity. 



Or the opposite change, expressed mechanically as ex- 

 pansion, will be evidenced by galvanometric positivity. But 

 it must be borne in mind that neither of these expressions 



Response by Method of Relative 

 Depression 



represents current of rest ; | represents 

 the action current. 





