﻿1875.] 
  Influence 
  of 
  Electricity 
  on 
  the 
  Hearts 
  of 
  Mollusks. 
  333 
  

  

  depending 
  on 
  the 
  fact 
  that 
  the 
  total 
  depressing 
  effect 
  of 
  the 
  current 
  

   on 
  the 
  rhythmically 
  beating 
  tissue 
  is 
  greater 
  than 
  the 
  total 
  exalting 
  

   effect. 
  

  

  It 
  may 
  seem 
  strange 
  to 
  speak 
  of 
  a 
  stimulus 
  as 
  producing 
  a 
  depressing 
  

   effect 
  ; 
  but 
  reflection 
  will 
  show 
  that 
  it 
  is 
  quite 
  what 
  ought 
  to 
  be 
  

   expected. 
  

  

  We 
  have 
  in 
  the 
  foregoing 
  contented 
  ourselves 
  with 
  speaking 
  of 
  the 
  

   tissue 
  in 
  the 
  neighbourhood 
  of 
  the 
  electrodes 
  as 
  being 
  in 
  a 
  kathodic 
  

   or 
  anodic 
  condition 
  as 
  the 
  case 
  may 
  be. 
  We 
  did 
  so 
  because, 
  not 
  

   having 
  examined 
  the 
  condition 
  of 
  the 
  electric 
  currents 
  of 
  the 
  ven- 
  

   tricle, 
  we 
  hesitated 
  in 
  using 
  the 
  terms 
  kathelectrotonus 
  and 
  anelectro- 
  

   tonus. 
  

  

  We 
  know, 
  however, 
  that 
  muscle 
  is 
  capable 
  of 
  being 
  thrown, 
  in 
  the 
  intra- 
  

   polar 
  region, 
  into 
  an 
  electrotonic 
  condition, 
  and 
  that 
  (quite 
  in 
  accordance 
  

   with 
  all 
  the 
  results 
  recorded 
  above) 
  this 
  condition 
  lasts 
  after 
  the 
  removal 
  

   of 
  the 
  current. 
  We 
  therefore 
  shall 
  probably 
  not 
  err 
  in 
  supposing 
  that 
  

   the 
  polarization 
  of 
  the 
  cardiac 
  tissue, 
  which 
  is 
  obviously 
  a 
  result 
  of 
  the 
  

   constant 
  current, 
  is 
  more 
  or 
  less 
  allied 
  to 
  that 
  kind 
  of 
  polarization 
  which 
  

   we 
  call 
  electrotonus. 
  

  

  ISTow 
  the 
  electrotonic 
  condition 
  of 
  nerve 
  or 
  muscle 
  differs 
  essentially 
  

   from 
  the 
  polarization 
  of 
  any 
  dead 
  matter 
  in 
  this, 
  that 
  it 
  is 
  essentially 
  a 
  

   function 
  of 
  the 
  vital 
  activity 
  of 
  the 
  substance 
  polarized. 
  May 
  we 
  interpret 
  

   this 
  as 
  meaning 
  that 
  the 
  change 
  in 
  muscle 
  or 
  nerve 
  which 
  constitutes 
  the 
  

   electrotonic 
  condition 
  is 
  brought 
  about 
  and 
  maintained, 
  not 
  solely 
  at 
  the 
  

   expense 
  of 
  the 
  energy 
  of 
  the 
  current, 
  but 
  also, 
  perhaps 
  chiefly, 
  at 
  the 
  

   expense 
  of 
  the 
  energy 
  of 
  the 
  tissue 
  itself! 
  

  

  If 
  so, 
  then 
  we 
  may 
  argue 
  that 
  while 
  in 
  the 
  normally 
  beating 
  heart 
  all 
  

   the 
  energy 
  of 
  the 
  tissue 
  is 
  used 
  for 
  the 
  production 
  of 
  the 
  beat, 
  when 
  a 
  

   constant 
  current 
  is 
  passed 
  through 
  it 
  some 
  of 
  this 
  energy, 
  in 
  addition 
  to 
  

   the 
  energy 
  of 
  the 
  current 
  itself, 
  is 
  used 
  in 
  establishing 
  anelectrotonus 
  

   and 
  kathelectrotonus. 
  There 
  must 
  therefore, 
  as 
  the 
  result 
  of 
  the 
  polari- 
  

   zation, 
  be 
  less 
  energy 
  (for 
  the 
  time 
  being) 
  available 
  for 
  the 
  purposes 
  of 
  

   pulsation. 
  

  

  The 
  idea 
  of 
  the 
  exalting 
  influence 
  of 
  a 
  stimulus 
  arises 
  naturally 
  from 
  

   the 
  fact 
  that 
  the 
  stimulus 
  may, 
  if 
  sufficiently 
  intense, 
  give 
  rise 
  to 
  a 
  con- 
  

   traction 
  ; 
  and 
  it 
  seems 
  at 
  first 
  sight 
  contradictory 
  that 
  one 
  and 
  the 
  same 
  

   thing 
  should 
  produce 
  apparently 
  exactly 
  opposite 
  effects. 
  

  

  It 
  is 
  very 
  easy, 
  however, 
  to 
  trace, 
  in 
  the 
  beating 
  ventricle 
  of 
  the 
  snail's 
  

   heart, 
  the 
  transition 
  from 
  inhibition 
  to 
  the 
  production 
  of 
  a 
  contraction 
  or 
  

   artificial 
  beat. 
  

  

  One 
  stage 
  in 
  this 
  transition 
  is 
  shown 
  in 
  fig. 
  4. 
  

  

  Here 
  a 
  weak 
  constant 
  current 
  passed 
  through 
  the 
  ventricle 
  longi- 
  

   tudinally 
  from 
  auricle 
  to 
  ventricle 
  (and 
  thus 
  most 
  favourable 
  for 
  inhibi- 
  

   tion) 
  caused, 
  when 
  the 
  passage 
  was 
  momentary 
  (i. 
  e. 
  was 
  removed 
  before 
  

   it 
  had 
  time 
  to 
  produce 
  its 
  full 
  effect, 
  and 
  thus 
  was 
  reduced, 
  so 
  to 
  speak, 
  

  

  