120 THE SIGNS OF LIFE [LECT. 



state. But the details of this effect require closer investigation 

 than I have yet found time to give to them. Thawed skin, 

 subsequent to congelation, has a greatly diminished resistance 

 e.g., a diminution to 50,000 ohms from an original resistance 

 of 1 50,000 ohms. 



Vegetable tissues likewise exhibit a very marked diminution 

 of resistance in consequence of excitation, and the diminution 

 is not solely a diminution of "contact resistance" at the elec- 

 trodes. It is internal or interpolar as well, owing probably 

 to a multiplication of electrolytes, possibly also to an actual 

 rupture of cell membranes. A very simple experiment will 

 serve to show you that the augmented conductivity is inter- 

 polar as well as polar. A flower stalk is laid across four 

 unpolarisable electrodes, E I I E, at 5 cm. intervals ; a tenth 

 of a volt is allowed to act upon the galvanometer through the 

 entire length of stalk E E, and through an intermediate portion 

 I I. The deflections indicate the current strength, and there- 

 fore the conductance of the corresponding lengths of stem. 

 Noting their values before and after tetanisation of the whole 

 stem through the terminal electrodes E E, you will find that 

 the conductance is augmented in the intermediate part I I, 

 showing that the alteration is not restricted to the contacts E E. 

 The conductance of I I, which was 0.8 y before the excitation 

 through E E, is raised to 2.0 y ; in E E itself, it has been raised 

 from 0.4 y to 1.6 y.* 



72. Du Bois experiment. - - The galvanometer is in its 

 usual position, with its magnets pointing N and S, and the 

 scale correspondingly arranged N and S ; you may consider that 

 the two ends of the scale represent the two terminals of the 

 galvanometer. I am seated facing you below the scale, with my 



* The symbol y denotes our unit of conductivity. (See Appendix, p. 169.) 

 The conductance and resistance in the above experiment are : 



of I I before 0.87 1.25 V. 



after 2.0 0.5 



E E before 0.4 2.5 



after 1.6 0.625 



