﻿1875.] 
  Influence 
  of 
  Electricity 
  on 
  the 
  Hearts 
  of 
  Mollusks. 
  339 
  

  

  ties, 
  joined 
  together 
  — 
  the 
  force 
  and 
  character 
  of 
  the 
  systole 
  and 
  the 
  length 
  

   of 
  the 
  diastole. 
  

  

  We 
  would 
  suggest 
  that 
  the 
  ganglia 
  are 
  not 
  automatic 
  in 
  function 
  in 
  

   the 
  above 
  sense, 
  but 
  simple 
  coordinators. 
  The 
  contractile 
  tissue 
  of 
  the 
  

   frog's 
  ventricle, 
  arranged 
  in 
  bundles 
  isolated 
  by 
  connective 
  tissue, 
  is 
  not 
  

   physiologically 
  continuous, 
  though 
  each 
  bundle 
  formed 
  by 
  the 
  opposition 
  

   of 
  branched 
  sheathless 
  muscular 
  fibres 
  may 
  be 
  continuous 
  throughout 
  

   itself 
  ; 
  and 
  the 
  consensus 
  we 
  spoke 
  of 
  just 
  now 
  cannot 
  be 
  effected 
  by 
  

   molecular 
  communications. 
  Hence 
  the 
  existence 
  of 
  differentiated 
  organs, 
  

   in 
  the 
  form 
  of 
  nerves 
  and 
  ganglia, 
  by 
  means 
  of 
  which 
  indications 
  of 
  the 
  

   condition 
  of 
  the 
  isolated 
  constituents 
  of 
  the 
  ventricle 
  (and, 
  we 
  may 
  add, 
  

   of 
  the 
  isolated 
  auricles 
  and 
  ventricle) 
  are 
  carried, 
  as 
  items 
  of 
  a 
  muscular 
  

   sense, 
  to 
  a 
  central 
  organ, 
  and 
  thus 
  the 
  state 
  of 
  each 
  part 
  is 
  made 
  common 
  

   to 
  all. 
  In 
  this 
  central 
  organ 
  the 
  advent 
  and 
  character 
  of 
  each 
  beat 
  is 
  

   determined 
  as 
  the 
  expression 
  of 
  the 
  nutritive 
  condition, 
  not 
  of 
  the 
  nerve- 
  

   cells 
  only, 
  but 
  of 
  the 
  contractile 
  elements 
  as 
  well. 
  

  

  If 
  this 
  view 
  of 
  the 
  function 
  of 
  automatic 
  ganglia 
  (which, 
  it 
  will 
  be 
  

   observed, 
  is 
  simply 
  a 
  modification 
  of 
  Sir 
  J. 
  Paget's 
  conception) 
  be 
  correct, 
  

   it 
  is 
  easy 
  to 
  understand 
  why 
  we 
  have 
  found 
  no 
  such 
  organs 
  in 
  the 
  phy- 
  

   siologically 
  continuous 
  protoplasmic 
  heart 
  of 
  the 
  snail. 
  

  

  It 
  needs 
  no 
  such 
  ganglia 
  for 
  the 
  carrying 
  on 
  of 
  its 
  own 
  rhythmic 
  beat 
  ; 
  

   nor 
  does 
  it 
  need 
  them 
  to 
  place 
  it 
  en 
  rapport 
  with 
  the 
  rest 
  of 
  the 
  body 
  of 
  the 
  

   animal. 
  The 
  movements 
  of 
  the 
  body 
  determine 
  the 
  quantity 
  of 
  blood 
  flow- 
  

   ing 
  to 
  the 
  heart 
  ; 
  the 
  force 
  and 
  rapidity 
  of 
  the 
  heart's 
  beat 
  is 
  in 
  direct 
  ratio 
  

   to 
  the 
  quantity 
  of 
  blood 
  distending 
  its 
  cavities 
  ; 
  and 
  thus 
  a 
  harmony 
  is 
  

   established 
  between 
  the 
  movements 
  of 
  the 
  body 
  and 
  the 
  circulation 
  quite 
  

   sufficient 
  for 
  the 
  purposes 
  of 
  the 
  snail's 
  life, 
  without 
  the 
  intervention 
  of 
  

   that 
  nervous 
  regulative 
  mechanism 
  supplied 
  to 
  the 
  vertebrate 
  heart 
  by 
  

   the 
  various 
  cardiac 
  ganglia, 
  the 
  pneumogastric, 
  and 
  other 
  nerves. 
  

  

  Resume. 
  

  

  "We 
  have 
  seen 
  that, 
  in 
  the 
  region 
  of 
  the 
  kathode, 
  a 
  condition 
  which 
  we 
  

   have 
  compared 
  with 
  the 
  kathelectro 
  tonus 
  of 
  nerves 
  is 
  set 
  up. 
  This 
  con- 
  

   dition 
  we 
  will 
  not 
  at 
  present 
  venture 
  to 
  characterize 
  more 
  closely 
  than 
  

   to 
  say 
  that 
  it 
  is 
  favourable 
  to 
  the 
  production 
  of 
  rhythmic 
  beats. 
  At 
  the 
  

   anode 
  precisely 
  the 
  opposite 
  effect 
  takes 
  place. 
  

  

  We 
  have 
  shown 
  that 
  both 
  conditions 
  require 
  some 
  time 
  for 
  their 
  com- 
  

   plete 
  establishment, 
  and 
  that 
  when 
  established 
  they 
  at 
  once 
  begin 
  to 
  

   decline. 
  Thus 
  they 
  speedily 
  reach 
  a 
  maximum 
  and 
  more 
  gradually 
  

   subside. 
  

  

  The 
  setting 
  up 
  of 
  kathelectrotonus 
  will, 
  if 
  sufficiently 
  intense 
  and 
  

   the 
  maximum 
  be 
  fairly 
  reached, 
  give 
  rise 
  to 
  a 
  contraction 
  or 
  beat. 
  The 
  

   giving 
  way 
  of 
  anelectrotonus, 
  though 
  with 
  less 
  ease, 
  will 
  also 
  cause 
  a 
  

   beat. 
  Both 
  the 
  establishment 
  of 
  anelectrotonus 
  and 
  the 
  disappearance 
  of 
  

   kathelectrotonus 
  are 
  unfavourable 
  to 
  the 
  production 
  of 
  the 
  rhythmic 
  beat. 
  

  

  