﻿1875.] 
  Influence 
  of 
  Electricity 
  on 
  the 
  Hearts 
  of 
  Mollusks. 
  335 
  

  

  and, 
  as 
  far 
  as 
  we 
  know, 
  the 
  heart 
  had 
  in 
  each 
  instance 
  been 
  treated, 
  in 
  

   some 
  way 
  or 
  other, 
  by 
  electric 
  currents. 
  

  

  We 
  are 
  totally 
  unable 
  to 
  give 
  any 
  explanation 
  of 
  the 
  phenomenon 
  ; 
  and 
  

   though 
  we 
  have 
  tried 
  in 
  various 
  ways 
  to 
  produce 
  it 
  artificially 
  at 
  will, 
  have 
  

   always 
  failed 
  to 
  do 
  so. 
  

  

  It 
  suggests 
  the 
  curious 
  inquiry 
  whether, 
  during 
  the 
  quiescent 
  periods, 
  

   the 
  heart 
  is 
  absolutely 
  at 
  rest, 
  or 
  in 
  reality 
  executing 
  pulsations 
  too 
  small 
  

   to 
  be 
  visible. 
  "We 
  have 
  been 
  unable 
  to 
  detect 
  any 
  indications 
  of 
  such 
  

   invisible 
  beats, 
  and 
  the 
  marked 
  length 
  of 
  the 
  first 
  and 
  last 
  diastole 
  in 
  each 
  

   active 
  phase 
  would 
  seem 
  to 
  indicate 
  that 
  the 
  median 
  portion 
  at 
  least 
  of 
  

   each 
  quiescent 
  phase 
  is 
  occupied 
  by 
  a 
  prolonged 
  diastole 
  of 
  absolute 
  

   quiescence. 
  

  

  We 
  might 
  further 
  speculate 
  as 
  to 
  whether 
  similar 
  secondary 
  rhythms, 
  

   marked, 
  not 
  of 
  course 
  by 
  absolute 
  quiescence, 
  but 
  by 
  a 
  more 
  or 
  less 
  pro- 
  

   nounced 
  rise 
  and 
  fall 
  of 
  cardiac 
  activity, 
  may 
  not 
  exist 
  under 
  normal 
  cir- 
  

   cumstances 
  — 
  whether 
  they 
  may 
  not, 
  for 
  instance, 
  be 
  diurnal 
  phases 
  of 
  the 
  

   heart's 
  own 
  nutrition 
  ; 
  and 
  also 
  as 
  to 
  whether 
  the 
  normal 
  pulse-phase 
  

   may 
  not 
  be 
  made 
  up 
  of 
  small, 
  more 
  rapid, 
  oscillations, 
  bearing 
  the 
  

   same 
  relation 
  to 
  it 
  as 
  it 
  does 
  to 
  the 
  larger 
  rhythm 
  we 
  are 
  speaking 
  of. 
  

  

  Lastly, 
  if 
  the 
  heart 
  of 
  the 
  snail 
  were 
  a 
  barrel-shaped 
  organ, 
  like 
  that 
  of 
  

   a 
  Tunicate, 
  with 
  each 
  end 
  equipollent 
  to 
  the 
  other, 
  instead 
  of 
  being 
  a 
  

   conical 
  mass 
  as 
  it 
  is, 
  with 
  a 
  wholly 
  preponderating 
  auricular 
  end, 
  it 
  is 
  

   easy 
  to 
  see 
  how 
  such 
  a 
  secondary 
  rhythm 
  as 
  the 
  one 
  we 
  have 
  described 
  

   would, 
  if 
  started 
  at 
  each 
  end 
  of 
  the 
  tube 
  at 
  different 
  times, 
  produce 
  the 
  

   well-known 
  alternating 
  action 
  so 
  characteristic 
  of 
  the 
  Tunicate 
  heart. 
  

  

  Experiments 
  on 
  the 
  Hearts 
  of 
  oilier 
  Mollusks. 
  

  

  The 
  foregoing 
  observations 
  on 
  the 
  heart 
  of 
  the 
  snail 
  were 
  made 
  by 
  us 
  

   together 
  in 
  the 
  Physiological 
  Laboratory 
  at 
  Cambridge. 
  

  

  During 
  a 
  stay 
  at 
  the 
  Zoological 
  Station 
  at 
  Naples, 
  in 
  the 
  month 
  of 
  

   November 
  last, 
  Mr. 
  Dew-Smith 
  made 
  several 
  observations 
  on 
  the 
  hearts 
  

   of 
  Sepia 
  and 
  Aplysia, 
  with 
  the 
  view 
  to 
  ascertain 
  whether 
  they 
  would 
  

   behave 
  towards 
  electric 
  currents 
  in 
  the 
  same 
  way 
  as 
  the 
  heart 
  of 
  the 
  

   snail. 
  We 
  hoped, 
  too, 
  they 
  perhaps 
  might 
  be 
  found 
  more 
  convenient 
  

   for 
  the 
  purposes 
  of 
  experiment 
  ; 
  this 
  hope, 
  however, 
  was 
  not 
  realized. 
  

  

  In 
  the 
  first 
  place 
  the 
  heart 
  of 
  the 
  Sepia, 
  though 
  it 
  will 
  beat 
  when 
  

   removed 
  from 
  the 
  body, 
  can 
  be 
  got 
  to 
  do 
  so 
  with 
  extreme 
  difficulty, 
  and 
  

   then 
  for 
  a 
  short 
  time 
  only. 
  The 
  observations 
  consequently 
  had 
  to 
  be 
  

   conducted 
  on 
  the 
  heart 
  in 
  situ, 
  and 
  for 
  this 
  reason, 
  as 
  was 
  explained 
  in 
  

   the 
  case 
  of 
  the 
  snail, 
  were 
  robbed 
  of 
  much 
  of 
  their 
  value. 
  

  

  Moreover 
  the 
  peculiar 
  shape 
  of 
  the 
  ventricle 
  of 
  the 
  Sepia's 
  heart, 
  with 
  

   its 
  two 
  aortse 
  and 
  its 
  two 
  branchial 
  sinuses, 
  render 
  it 
  much 
  less 
  suitable 
  

   for 
  the 
  purpose 
  in 
  hand 
  than 
  the 
  more 
  compact 
  and 
  simple 
  ventricle 
  of 
  

   the 
  snail. 
  

  

  Nevertheless 
  the 
  following 
  results 
  were 
  arrived 
  at 
  ; 
  — 
  

  

  