TENSION PHENOMKNA OF LIVING ELEMENTS. 



change is accompanied for immediately preceded) by increase in 

 permeability of the plasma membrane to anions. Burdon- 

 Sanderson states that, whereas the m< >\vment resulting from 

 turgor change begins 2.5 seconds after stimulation, the negative 

 variation reaches its maximum I second after simulation. This 

 max In- due to the mechanical inertia, or the time required for 

 the diffusion of substances. 



It ua- sated in the preceding chapter that light change- the 

 permeability of the plasma membrane, and Waller 1 found cor- 

 responding electrical changes due to light, but not al\va\- in the 

 same direction in different plants. This inconstancy in direction 

 is probably due to the fact that light not only influences the 

 I -i i mi abilitx , but also the assimilation, and changes in a imi- 

 laiioii produce electric changes. This is supported by the fact- 

 thai i >IH rtoii- found that assimilation as well as electric chai 

 i- uios affected by the longer light rays. 



2. In Muscle and Xerve. 3 



i >s \\ald' proposed the hypothesis that the electric pin noniena 

 ot must le, nerve and the electric organs of fish (which mav n -at h 

 se\eral hum lud volts) are produced with the aid of semiper- 

 meable membranes. The alternative theory of Hermann, \\hich 

 \\oiild account for the current of injury by assuming the pn>- 

 oi some electrolyte (alkali?) in the wounded region. \\h"-' 

 - and kaiions have very different speeds, >eem- le , ]nb- 

 .ibl\ to be i he correct one. 



\. c. .j-diii^ to the "membrane theory," the muscle or net \ e 

 eleineiii i-- surrounded by a semipermeablc membraiu- allo\\iu^ 

 easier passage to kations than to anions. The kaii./n- ua in- 

 through the membrane are held back by the ne-ati\e field pro- 

 duced by the confined anions, but owing to their kinetic energy, 

 the kation- pa-s out far enough to give the outside of the cell 

 -in lace a i io-i t ive charge. Therefore an \ portion of the siirfai 

 that i- made freely permeable to anion> become- electronegative 



Jota 1 l:\aiol.. iSgg-'oo, XXV., 18. 



ntiilniti.ni a lYtude du mode de la production <!' l' l-i trii it. 'Ian- <-tres 

 \i\anii-. I r.i.,nt\ ,1,- 1'hfititnt Solvay. 1902, \'. 



R 1 LHie, .1".-.;. .'ur. Physiol., ign. XXN'III.. 1.^7. 



* /.fit. /-/IVV/A-. L'h,-IH.. I Soc.. \'I.. 71. 



