﻿Work 
  Measured 
  by 
  the 
  Discharge 
  of 
  Carbon 
  Dioxide. 
  169 
  

  

  increased 
  pumping 
  out 
  of 
  CO2 
  by 
  the 
  lungs 
  and 
  increased 
  muscular 
  meta- 
  

   bolism 
  ; 
  but 
  as 
  time 
  passes, 
  the 
  CO2 
  output 
  reaches 
  a 
  maximum, 
  and 
  a 
  

   constant 
  regime 
  is 
  established, 
  during 
  which 
  the 
  CO2 
  ordinate 
  serves 
  as 
  a 
  

   true 
  physiological 
  indicator 
  of 
  muscular 
  metabolism. 
  This 
  constant 
  regime 
  

   is 
  reached 
  very 
  rapidly, 
  i.e., 
  in 
  a 
  very 
  few 
  minutes 
  — 
  certainly 
  in 
  five 
  minutes, 
  

   sometimes 
  even 
  less 
  — 
  and 
  while 
  it 
  lasts, 
  the 
  CO2 
  ordinate 
  is 
  a 
  faithful 
  

   indicator 
  of 
  the 
  internal 
  physiological 
  activity. 
  During 
  the 
  constant 
  regime 
  

   of 
  deeper 
  breathing 
  caused 
  by 
  work, 
  the 
  physiological 
  order 
  of 
  events 
  is 
  (1) 
  

   increased 
  production 
  of 
  C0 
  2 
  causing 
  (2) 
  greater 
  thoracic 
  movements 
  by 
  which 
  

   the 
  increase 
  is 
  got 
  rid 
  of. 
  With 
  the 
  increased 
  ventilation 
  there 
  is 
  of 
  course 
  

   increased 
  pump 
  action, 
  and 
  both 
  these 
  factors 
  are 
  equally 
  physiological, 
  in 
  

   as 
  much 
  as 
  both 
  are 
  excited 
  by 
  the 
  state 
  which 
  they 
  serve 
  to 
  relieve. 
  

  

  And 
  so 
  the 
  muscular 
  metabolism 
  of 
  a 
  workman 
  at 
  steady 
  work 
  — 
  preferably 
  

   piece-work 
  — 
  is 
  usefully 
  measured 
  by 
  short 
  samples 
  of 
  expired 
  air 
  from 
  which 
  

   his 
  " 
  CO2 
  ordinate," 
  i.e., 
  his 
  established 
  rate 
  of 
  CO2 
  discharge, 
  is 
  ascertained. 
  

   The 
  procedure 
  has 
  two 
  principal 
  advantages 
  : 
  (1) 
  The 
  interruption 
  of 
  work 
  is 
  

   trifling 
  ; 
  it 
  is, 
  e.g., 
  cheerfully 
  tolerated 
  by 
  piece-workers, 
  to 
  whom 
  time 
  is 
  

   money 
  ; 
  (2) 
  The 
  sampling 
  is 
  taken 
  under 
  actual 
  conditions 
  of 
  work, 
  and 
  as 
  

   nearly 
  as 
  possible 
  during 
  work. 
  Work 
  done 
  in 
  a 
  respiration 
  chamber, 
  or 
  for 
  

   a 
  few 
  minutes 
  for 
  the 
  sake 
  of 
  affording 
  a 
  sample, 
  cannot 
  be 
  regarded 
  as 
  

   normal 
  or 
  as 
  affording 
  a 
  fair 
  sample 
  of 
  the 
  respiratory 
  activity 
  obtaining 
  

   during 
  normal 
  work. 
  

  

  As 
  is 
  shown 
  in 
  this 
  preliminary 
  report, 
  the 
  constant 
  regime 
  during 
  work 
  

   is 
  established 
  at 
  the 
  beginning 
  of 
  work 
  and 
  disestablished 
  at 
  the 
  end 
  of 
  work 
  

   with 
  surprising 
  rapidity. 
  Samples 
  should 
  not 
  be 
  taken 
  during 
  either 
  of 
  these 
  

   periods 
  of 
  change. 
  They 
  should 
  be 
  taken 
  if 
  possible 
  without 
  interruption 
  of 
  

   work 
  in 
  progress, 
  or 
  if 
  this 
  should 
  be 
  impossible, 
  with 
  least 
  interruption 
  for 
  

   the 
  shortest 
  practicable 
  periods 
  — 
  20 
  to 
  30 
  seconds 
  — 
  immediately 
  after 
  the 
  

   load 
  or 
  tool 
  has 
  been 
  dropped 
  as, 
  e.g., 
  in 
  the 
  carrying 
  of 
  coal 
  or 
  grain 
  or 
  meat, 
  

   which 
  form 
  the 
  hardest 
  labour 
  going 
  on 
  in 
  the 
  London 
  docks. 
  An 
  obvious 
  

   drawback 
  to 
  short 
  sampling 
  is, 
  of 
  course, 
  the 
  possible 
  error 
  arising 
  from 
  

   turning 
  the 
  tap 
  at 
  beginning 
  and 
  end 
  of 
  say 
  30 
  seconds 
  during 
  different 
  

   phases 
  of 
  respiration. 
  This 
  error 
  is 
  to 
  be 
  avoided 
  by 
  turning 
  the 
  tap 
  on 
  and 
  

   off 
  at 
  the 
  same 
  phase, 
  i.e., 
  immediately 
  after 
  expiration. 
  In 
  the 
  mouthpiece 
  

   which 
  I 
  prefer, 
  the 
  expiratory 
  valve 
  click 
  is 
  easy 
  to 
  follow, 
  and 
  I 
  have 
  not 
  

   found 
  any 
  disturbance 
  of 
  the 
  subject 
  to 
  be 
  caused 
  by 
  the 
  valve 
  clicking, 
  as 
  has 
  

   been 
  reported 
  by 
  some 
  observers. 
  For 
  a 
  subject 
  breathing 
  say 
  15 
  per 
  minute, 
  

   it 
  is 
  2 
  to 
  1 
  against 
  the 
  tap 
  being 
  closed 
  during 
  the 
  expiratory 
  movement 
  ; 
  

   but 
  if 
  this 
  should 
  happen, 
  a 
  considerable 
  error, 
  amounting 
  to 
  perhaps 
  10 
  per 
  

   cent., 
  might 
  be 
  made 
  in 
  a 
  half-minute 
  sample. 
  

  

  