﻿326 
  Dr. 
  M. 
  Foster 
  and 
  Mr. 
  A. 
  Gr. 
  Dew-Smith 
  on 
  the 
  [Mar. 
  18, 
  

  

  The 
  absence 
  of 
  a 
  beat 
  on 
  a 
  momentary 
  application 
  might 
  be 
  explained 
  

   by 
  supposing 
  that 
  the 
  effect 
  of 
  the 
  too 
  rapidly 
  succeeding 
  break 
  inter- 
  

   feres 
  with 
  the 
  effect 
  of 
  the 
  immediately 
  preceding 
  make. 
  But, 
  on 
  the 
  

   one 
  hand, 
  we 
  have 
  no 
  positive 
  indication 
  of 
  the 
  possibility 
  of 
  such 
  an 
  in- 
  

   terference 
  (and 
  there 
  are 
  reasons 
  for 
  thinking 
  it 
  extremely 
  unlikely), 
  

   while 
  the 
  normal 
  character 
  of 
  the 
  kathodic 
  beat, 
  when 
  it 
  does 
  occur 
  with 
  

   a 
  'stronger 
  current, 
  distinctly 
  opposes 
  such, 
  a 
  view. 
  On 
  the 
  other 
  hand, 
  

   a 
  distinct 
  interval 
  does 
  exist 
  between 
  the 
  making 
  of 
  the 
  circuit 
  and 
  the 
  

   commencement 
  of 
  the 
  contraction, 
  an 
  interval 
  easily 
  recognizable 
  by 
  the 
  

   eye, 
  though, 
  in 
  the 
  absence 
  of 
  any 
  graphic 
  method, 
  we 
  have 
  been 
  unable 
  

   to 
  measure 
  it. 
  "We 
  conclude, 
  therefore, 
  that, 
  in 
  order 
  to 
  produce 
  the 
  

   maximum 
  effect 
  of 
  even 
  the 
  making 
  kathodic 
  beat, 
  a 
  certain 
  time 
  

   is 
  required. 
  This 
  time 
  is 
  longer 
  for 
  weak 
  currents 
  than 
  for 
  strong 
  ; 
  and 
  

   currents 
  sufficiently 
  weak 
  may 
  be 
  applied 
  for 
  a 
  short 
  time 
  without 
  pro- 
  

   ducing 
  any 
  beat, 
  the 
  maximum 
  effect 
  not 
  having 
  time 
  to 
  develop 
  itself, 
  

   though 
  the 
  beat 
  does 
  appear 
  when 
  the 
  action 
  of 
  the 
  same 
  current 
  is 
  

   prolonged. 
  

  

  Sufficient 
  time 
  being 
  allowed 
  for 
  the 
  production 
  of 
  the 
  beat, 
  the 
  strength 
  

   of 
  the 
  kathodic 
  making-beat 
  will 
  depend 
  otherwise 
  entirely 
  on 
  the 
  strength 
  

   of 
  the 
  current 
  (the 
  irritability 
  of 
  the 
  tissues 
  of 
  the 
  ventricle 
  being 
  sup- 
  

   posed 
  to 
  be 
  constant). 
  

  

  The 
  strength 
  of 
  the 
  anodic 
  breaking-beat 
  depends, 
  however, 
  in 
  a 
  pecu- 
  

   liar 
  way 
  on 
  the 
  duration 
  of 
  the 
  current. 
  Up 
  to 
  a 
  certain 
  point 
  the 
  more 
  

   prolonged 
  the 
  action 
  of 
  current 
  the 
  stronger 
  is 
  the 
  anodic 
  beat 
  ; 
  but 
  a 
  

   limit 
  is 
  soon 
  reached, 
  after 
  which 
  the 
  strength 
  of 
  the 
  anodic 
  beat 
  is 
  dimi- 
  

   nished 
  by 
  further 
  prolongation 
  of 
  the 
  action 
  of 
  the 
  current. 
  We 
  have 
  

   not 
  gone 
  into 
  this 
  point 
  fully, 
  but 
  the 
  result 
  is 
  evidently 
  connected 
  with 
  

   a 
  so-called 
  " 
  exhaustion 
  " 
  of 
  the 
  tissue. 
  

  

  "We 
  have 
  called 
  the 
  contraction 
  which 
  takes 
  place 
  at 
  the 
  make 
  or 
  break 
  

   " 
  a 
  beat." 
  We 
  think 
  we 
  are 
  justified 
  in 
  giving 
  it 
  this 
  name, 
  though 
  it 
  

   differs, 
  as 
  we 
  have 
  pointed 
  out, 
  from 
  the 
  normal 
  beat 
  in 
  some 
  particulars. 
  

   Our 
  strongest 
  reason 
  for 
  doing 
  so 
  is 
  as 
  follows 
  : 
  — 
  

  

  When 
  the 
  ventricle 
  and 
  auricle 
  are 
  placed 
  between 
  the 
  electrodes, 
  so 
  

   that 
  the 
  kathode 
  is 
  against 
  the 
  auricle 
  and 
  the 
  anode 
  against 
  the 
  aortic 
  

   end 
  of 
  the 
  ventricle, 
  the 
  kathodic 
  making-beat 
  isfolloived 
  by 
  a 
  second, 
  by 
  

   a 
  third, 
  and 
  by 
  sometimes 
  severed 
  beats, 
  all 
  kathodic 
  in 
  their 
  features, 
  i. 
  e. 
  

   starting 
  from 
  the 
  kathode 
  and 
  travelling 
  towards 
  the 
  anode. 
  In 
  other 
  

   words, 
  a 
  rhythmic 
  pulsation 
  is 
  set 
  going 
  at 
  the 
  kathodic 
  end. 
  

  

  It 
  is 
  impossible 
  to 
  regard 
  these 
  beats 
  as 
  simple 
  contractions 
  caused 
  by 
  

   the 
  stimulus-wave, 
  started, 
  like 
  the 
  stimulus-wave 
  in 
  a 
  nerve, 
  by 
  the 
  

   establishment 
  of 
  kathelectrotonus. 
  They 
  are 
  evidently 
  actual 
  beats, 
  whose 
  

   occurrence 
  is 
  favoured 
  by 
  the 
  conditions 
  brought 
  about 
  by 
  the 
  action 
  of 
  

   the 
  current 
  (fig. 
  10, 
  p. 
  343.). 
  

  

  Of 
  these 
  the 
  first 
  (the 
  ordinary 
  making-beat) 
  is 
  always 
  (as 
  far 
  as 
  we 
  

   have 
  seen) 
  the 
  strongest. 
  The 
  succeeding 
  ones 
  diminish 
  in 
  intensity, 
  

  

  