﻿1875.] 
  Influence 
  of 
  Electricity 
  on 
  the 
  Hearts 
  of 
  Mollusks. 
  341 
  

  

  Fig. 
  3. 
  Constant 
  current 
  applied 
  to 
  a 
  spontaneously 
  beating 
  ventricle. 
  

  

  The 
  upper 
  line 
  indicates 
  the 
  beats 
  of 
  the 
  ventricle, 
  the 
  middle 
  line 
  the 
  appli- 
  

   cation 
  of 
  the 
  current. 
  The 
  kathode 
  was 
  placed 
  at 
  the 
  aortic 
  end 
  of 
  the 
  ventricle, 
  

   anode 
  placed 
  at 
  the 
  auricular 
  end 
  of 
  the 
  ventricle. 
  No 
  resistance 
  in 
  the 
  resist- 
  

   ance-shunt 
  ; 
  consequently 
  only 
  the 
  very 
  smallest 
  fraction 
  of 
  the 
  current 
  could 
  

   have 
  passed 
  through 
  the 
  ventricle. 
  Current 
  made 
  at 
  x 
  and 
  broken 
  at 
  y. 
  

   The 
  beat 
  a 
  started 
  from 
  the 
  aortic 
  end, 
  the 
  beat 
  (3 
  from 
  the 
  auricular 
  end. 
  

  

  Fig. 
  4. 
  The 
  same 
  current, 
  applied 
  to 
  the 
  same 
  heart, 
  under 
  exactly 
  similar 
  circumstances 
  

   as 
  in 
  fig. 
  3, 
  except 
  that 
  the 
  break 
  almost 
  instantaneously 
  followed 
  the 
  make. 
  

   No 
  beat 
  was 
  produced, 
  but 
  only 
  a 
  lengthening 
  of 
  the 
  diastole 
  a. 
  

  

  Fig. 
  5. 
  Effect 
  of 
  constant 
  current 
  applied 
  to 
  the 
  spontaneously 
  beating 
  heart, 
  the 
  

   auricle 
  still 
  attached 
  to 
  ventricle. 
  Kathode 
  at 
  auricle, 
  anode 
  at 
  aortic 
  end 
  of 
  

   ventricle. 
  Resistance 
  introduced 
  into 
  the 
  resistance-shunt 
  nil 
  ; 
  consequently 
  the 
  

   vei*y 
  feeblest 
  current 
  was 
  sent 
  through 
  the 
  heart. 
  The 
  current 
  is 
  made 
  at 
  x 
  aud 
  

   broken 
  at 
  y. 
  No 
  appreciable 
  effect 
  during 
  the 
  passage 
  of 
  the 
  current, 
  except 
  a 
  

   slight 
  quickening 
  of 
  the 
  beat. 
  The 
  breaking 
  of 
  the 
  current 
  is 
  marked 
  by 
  the 
  

   prolonged 
  diastole 
  at 
  a. 
  

  

  Fig. 
  6. 
  Example 
  of 
  the 
  " 
  secondary 
  rhythm 
  " 
  of 
  the 
  ventricle 
  of 
  the 
  snail's 
  heart. 
  

  

  Shows 
  the 
  secondary 
  rhythm 
  spoken 
  of 
  on 
  page 
  334. 
  The 
  last 
  of 
  a 
  series 
  of 
  

   9 
  beats 
  is 
  shown 
  at 
  a. 
  Then 
  follows 
  a 
  pause 
  (/3) 
  for 
  18 
  seconds 
  ; 
  then 
  the 
  beats 
  

   recommence 
  at 
  y, 
  going 
  on 
  9 
  times 
  to 
  8 
  ; 
  then 
  again 
  follows 
  the 
  pause 
  e, 
  suc- 
  

   ceeded 
  by 
  another 
  series 
  of 
  9 
  beats, 
  commencing 
  at 
  £. 
  

  

  Fig. 
  7. 
  Inhibition 
  of 
  ventricle 
  by 
  constant 
  current 
  thrown 
  in 
  during 
  an 
  active 
  period 
  

   of 
  the 
  secondary 
  rhythm 
  shown 
  in 
  fig. 
  6. 
  

  

  Auricle 
  still 
  attached 
  to 
  ventricle, 
  and 
  '1 
  ohm 
  introduced 
  into 
  the 
  resistance- 
  

   shunt. 
  The 
  anode 
  at 
  the 
  auricle, 
  the 
  kathode 
  at 
  the 
  aortic 
  end 
  of 
  the 
  ventricle. 
  

   An 
  instantaneous 
  make 
  and 
  break, 
  whether 
  thrown 
  in 
  during 
  the 
  period 
  of 
  rest 
  

   or 
  during 
  the 
  period 
  of 
  activity, 
  produced 
  no 
  effect, 
  a 
  is 
  the 
  first 
  of 
  the 
  series 
  

   of 
  beats 
  succeeding 
  a 
  pause. 
  On 
  the 
  making 
  of 
  the 
  current 
  at 
  x 
  the 
  beats 
  cease, 
  

   but 
  reappear 
  at 
  j3 
  upon 
  the 
  breaking 
  of 
  the 
  current 
  at 
  y. 
  

  

  N.B. 
  The 
  point 
  of 
  the 
  lever 
  marking 
  the 
  ventricular 
  beats 
  on 
  the 
  upper 
  line 
  

   was 
  not 
  placed 
  exactly 
  over 
  the 
  point 
  of 
  the 
  lever 
  marking 
  on 
  the 
  middle 
  line 
  

   the 
  application 
  of 
  the 
  current, 
  consequently 
  the 
  beat 
  j3 
  seems 
  to 
  precede 
  the 
  

   breaking 
  of 
  the 
  current 
  at 
  y. 
  In 
  reality 
  it 
  succeeded 
  it 
  by 
  a 
  very 
  short 
  interval. 
  

  

  Fig. 
  8. 
  Pulsation 
  brought 
  on 
  by 
  constant 
  current 
  thrown 
  in 
  during 
  the 
  resting-period 
  

   of 
  secondary 
  rhythm. 
  

  

  Heart 
  and 
  strength 
  of 
  current 
  same 
  as 
  in 
  fig. 
  7. 
  Kathode 
  at 
  auricle, 
  anode 
  at 
  

   aortic 
  end 
  of 
  ventricle. 
  The 
  resting-period 
  or 
  pause 
  is 
  seen 
  commencing 
  at 
  a, 
  

   but 
  is 
  broken 
  by 
  the 
  beat 
  j3, 
  induced 
  by 
  the 
  constant 
  current, 
  which 
  is 
  made 
  

   at 
  x 
  ; 
  the 
  beats 
  continue, 
  ceasing 
  at 
  y 
  when 
  the 
  current 
  is 
  broken 
  at 
  y. 
  

  

  Fig. 
  9. 
  Constant 
  current 
  applied 
  to 
  the 
  heart 
  at 
  rest. 
  

  

  Auricle 
  still 
  attached 
  to 
  the 
  ventricle. 
  Anode 
  at 
  the 
  auricle, 
  kathode 
  at 
  the 
  

   aortic 
  end 
  of 
  the 
  ventricle. 
  The 
  resistance 
  in 
  the 
  resistance- 
  shunt 
  amounted 
  to 
  

   1 
  ohm. 
  Otherwise 
  the 
  arrangements 
  were 
  the 
  same 
  as 
  in 
  fig. 
  12 
  &c. 
  The 
  

   beat 
  a 
  was 
  very 
  faint, 
  starting 
  from 
  the 
  aortic 
  end 
  of 
  the 
  ventricle. 
  The 
  beats 
  

   (3, 
  y 
  started 
  from 
  the 
  auricular 
  end 
  of 
  the 
  ventricle. 
  This 
  was 
  an 
  exceptional 
  

   case, 
  in 
  which 
  a 
  beat 
  (/3) 
  appeared 
  before 
  the 
  breaking 
  of 
  the 
  current. 
  

  

  Fig. 
  10. 
  Constant 
  current. 
  

  

  Applied 
  to 
  heart 
  at 
  rest. 
  Kathode 
  at 
  auricle, 
  anode 
  at 
  aortic 
  end 
  of 
  ventricle. 
  

   The 
  top 
  line 
  indicates 
  beat 
  of 
  ventricle 
  ; 
  the 
  middle 
  line 
  indicates 
  the 
  applica- 
  

   tion 
  of 
  the 
  current, 
  made 
  at 
  x 
  and 
  broken 
  at 
  y. 
  A 
  single 
  Daniell's 
  cell 
  was 
  used. 
  

   In 
  the 
  resistance-shunt 
  the 
  resistance 
  was 
  1 
  ohm 
  ; 
  consequently 
  a 
  small 
  fraction 
  

   only 
  of 
  the 
  total 
  current 
  passed 
  through 
  the 
  heart. 
  

  

  