﻿340 
  Dr. 
  M. 
  Foster 
  and 
  Mr. 
  A. 
  G. 
  Dew-Smith 
  on 
  the 
  [Mar. 
  18, 
  

  

  Thus 
  the 
  effect 
  produced 
  by 
  a 
  coustaut 
  current 
  at 
  each 
  pole 
  is 
  mixed, 
  

   being 
  partly 
  favourable 
  and 
  partly 
  unfavourable 
  to 
  a 
  beat. 
  

  

  The 
  total 
  effect 
  of 
  the 
  passage 
  of 
  a 
  current, 
  whether 
  a 
  contraction 
  be 
  

   called 
  forth 
  or 
  not, 
  is 
  unfavourable 
  to 
  the 
  rhythmic 
  beat; 
  and 
  when 
  

   currents 
  too 
  weak 
  or 
  of 
  too 
  short 
  duration 
  to 
  produce 
  a 
  visible 
  contrac- 
  

   tion 
  are 
  employed, 
  the 
  unfavourable 
  effect 
  alone 
  becomes 
  evident. 
  

  

  When 
  the 
  brief 
  passage 
  of 
  a 
  weak 
  current 
  is 
  followed 
  at 
  a 
  sufficiently 
  

   short 
  interval 
  by 
  a 
  similar 
  brief 
  passage, 
  the 
  unfavourable 
  effects 
  are, 
  in 
  

   a 
  measure, 
  added 
  together 
  ; 
  and 
  thus, 
  by 
  repetition, 
  a 
  cumulative 
  result 
  

   is 
  reached. 
  

  

  Hence 
  it 
  is 
  that 
  a 
  single 
  induction-shock, 
  too 
  weak 
  in 
  itself 
  to 
  pro- 
  

   duce 
  either 
  a 
  contraction 
  or 
  such 
  a 
  prolongation 
  of 
  the 
  diastole 
  as 
  can 
  be 
  

   satisfactorily 
  measured, 
  will, 
  if 
  repeated 
  rapidly 
  enough, 
  produce 
  an 
  un- 
  

   mistakable 
  inhibition. 
  

  

  How 
  far 
  the 
  observations 
  we 
  have 
  made, 
  and 
  the 
  explanations 
  we 
  have 
  

   offered, 
  can 
  be 
  regarded 
  as 
  throwing 
  any 
  light 
  on 
  the 
  working 
  of 
  the 
  

   vertebrate 
  heart 
  and 
  on 
  the 
  general 
  theory 
  of 
  inhibition, 
  must 
  be 
  deter- 
  

   mined 
  by 
  further 
  inquiries. 
  These 
  we 
  have 
  already 
  commenced, 
  and 
  hope 
  

   before 
  long 
  to 
  lay 
  some 
  of 
  our 
  results 
  before 
  the 
  Society. 
  

  

  EXPLANATION 
  OF 
  THE 
  DIAGRAMS 
  (pp. 
  342, 
  343). 
  

   They 
  are 
  all 
  to 
  be 
  read 
  from 
  right 
  to 
  left. 
  

  

  Each 
  figure 
  consists 
  (except 
  in 
  the 
  case 
  of 
  fig. 
  6) 
  of 
  three 
  lines. 
  Of 
  these, 
  one, 
  gene- 
  

   rally 
  the 
  upper, 
  indicates 
  the 
  application 
  of 
  the 
  stimulus. 
  

  

  In 
  the 
  case 
  of 
  single 
  induction-shocks, 
  as 
  in 
  figs. 
  1 
  & 
  2, 
  the 
  descent 
  of 
  the 
  line 
  indi- 
  

   cates 
  the 
  making, 
  the 
  ascent 
  the 
  breaking 
  of 
  the 
  primary 
  current. 
  Inasmuch 
  as 
  the 
  

   making-shock 
  was 
  alone 
  employed, 
  the 
  breaking-shock 
  being 
  stopped, 
  the 
  descent 
  in 
  

   these 
  figures 
  alone 
  indicates 
  stimulation. 
  

  

  In 
  figs. 
  3-13 
  the 
  ascent 
  in 
  the 
  line, 
  generally 
  indicated 
  by 
  x, 
  marks 
  the 
  making, 
  and 
  

   the 
  descent, 
  generally 
  marked 
  y, 
  indicates 
  the 
  breaking 
  of 
  the 
  current. 
  

  

  The 
  middle 
  line 
  (unless 
  otherwise 
  mentioned) 
  indicates 
  the 
  beat 
  of 
  the 
  ventricle. 
  

  

  In 
  figs. 
  1-8 
  the 
  ascent, 
  and 
  in 
  figs. 
  9-13 
  the 
  descent, 
  marks 
  the 
  commencement 
  of 
  

   the 
  beat. 
  

  

  In 
  no 
  case 
  does 
  the 
  interval 
  between 
  the 
  ascent 
  and 
  descent 
  in 
  figs. 
  1-8, 
  or 
  descent 
  

   and 
  ascent 
  in 
  figs. 
  9-13, 
  in 
  any 
  way 
  correspond 
  to 
  the 
  length 
  of 
  the 
  ventricular 
  

   systole. 
  

  

  The 
  marks 
  on 
  the 
  bottom 
  line 
  in 
  each 
  figure 
  indicate 
  seconds. 
  

   Fig. 
  1. 
  Repeated 
  single 
  induction-shocks. 
  

  

  Two 
  shocks 
  thrown 
  in 
  at 
  x 
  causing 
  distinct 
  prolongation 
  of 
  diastole 
  a, 
  then 
  

   followed 
  a 
  very 
  feeble 
  beat, 
  then 
  two 
  more 
  shocks 
  at 
  y, 
  followed 
  again 
  by 
  pro- 
  

   longation 
  of 
  diastole 
  (3. 
  The 
  stimulations 
  were 
  produced 
  by 
  a 
  Du 
  Bois-Rey- 
  

   mond's 
  induction-apparatus, 
  worked 
  by 
  one 
  Daniell's 
  cell. 
  The 
  secondary 
  coil 
  

   at 
  8°. 
  The 
  making-shock 
  only 
  was 
  used. 
  

   Fig. 
  2. 
  Single 
  induction-shock. 
  

  

  Single 
  induction-shock 
  thrown 
  in 
  at 
  x, 
  after 
  a 
  series 
  of 
  normal 
  beats. 
  The 
  

   result 
  was 
  distinct 
  inhibition 
  for 
  a 
  time, 
  then 
  followed 
  a 
  feeble 
  beat 
  at 
  a, 
  then 
  

   another 
  shock 
  was 
  thrown 
  in 
  at 
  y, 
  followed 
  by 
  a 
  pause. 
  At 
  j3 
  the 
  heart 
  com- 
  

   menced 
  to 
  beat 
  again, 
  and 
  resisted 
  the 
  influence 
  of 
  the 
  three 
  succeeding 
  shocks 
  

   thrown 
  in, 
  continuing 
  to 
  beat 
  normally. 
  Making-shock 
  only. 
  One 
  Daniell's 
  

   cell. 
  Coil 
  at 
  5°. 
  

  

  