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ME.  J.  LISTEE  ON  THE  PAETS  OE  THE  NEETOHS  SYSTEM 
From  the  analogy  of  the  intestinal  and  cardiac  movements*,  it  is  probable  that  the 
local  coordinating  apparatus  for  the  arteries  comes  into  play  in  all  cases  of  arterial  con- 
traction in  the  living  animal,  and  is  the  medium  through  which  the  nerves  which  arise 
from  the  cord  act  upon  the  vessels.  But  it  is  very  important  to  bear  in  mind  that  it  is, 
under  ordinary  circumstances,  in  entire  subjection  to  the  spinal  system,  and  only  acts 
independently  under  special  conditions  of  local  irritation. 
It  remained  as  yet  undecided  whether  the  nervous  centre  for  the  arteries  contained  in 
the  cerebro-spinal  axis  were  extensively  diffused  or  limited  to  some  particular  region  of 
it.  The  experiments  hitherto  related  had  revealed  nothing  absolutely  iiTeconcileable 
with  the  hypothesis  of  a spot  about  the  middle  of  the  cord  being  the  special  regulator 
of  the  contractions  of  the  vessels;  a view  indicated,  though  by  no  means  proved,  as 
regards  the  arteries  of  the  face  and  fore-hmbs  in  Mammalia,  by  the  observations  of 
Wallee  and  Budge  and  of  Schiff,  alluded  to  at  the  commencement  of  this  paper.  It 
appeared  probable  that  this  point  might  be  readily  determined  by  removing  the  middle 
third  of  the  cord,  and  ascertaining  whether  or  not  the  arteries  still  retained  their  con- 
tractility f.  Accordingly,  on  the  26th  of  August,  1857,  having  selected  for  measurement 
an  artery  in  one  of  the  webs  of  a frog,  I divided  the  cord  transversely  at  the  distance  of 
a quarter  of  its  length  from  the  posterior  end,  at  11**  7“  a.m.  During  the  next  half- 
hour  the  diameter  of  the  vessel  was  observed  varying  frequently  from  to  1^°.  At 
Ifh  34m  again  cut  across  opposite  the  middle  of  the  scapulae,  ?.  e.  at  a 
distance  of  a little  more  than  a quarter  of  its  length  from  the  occiput.  After  this  opera- 
tion the  artery  was  observed  for  about  a quarter  of  an  hour  varying  occasionally  in  cahbre 
between  1°  and  2°.  At  11**  53***  the  portion  of  cord  intervening  between  the  two  trans- 
verse incisions,  and  measuring  very  nearly  half  its  entire  length,  was  removed,  imme- 
diately after  which  the  artery  measured  1^°.  At  11**  55***  its  diameter  was  1°,  the  heart 
meanwhile  continuing  in  good  action,  and  twelve  minutes  later  the  vessel  was  agam  seen 
to  change  in  calibre  from  1°  to  1^°  and  back  again  to  1°.  The  heart’s  action  after- 
wards became  very  feeble,  and  the  parts  of  the  nervous  centres  concerned  in  regulating 
the  arterial  calibre  appeared  also  to  be  failing  in  their  functions,  the  vessel  vailing  very 
slightly,  and  gradually  increasing  in  diameter,  till  towards  1**  p.m.  its  measurements 
were  from  2°  to  At  1**  1***  the  posterior  end  of  the  cord  was  removed,  immediately 
after  which  the  diameter  of  the  artery  was  above  2-^°,  or  larger  than  ever  seen  before ; 
at  1*“  4***  it  was  near  2^°,  and  continued  so  at  1**  10***.  Soon  after  this  the  cii-culation 
ceased  entirely. 
In  this  case,  notwithstanding  the  removal  of  the  two  middle  quarters  of  the  cord,  the 
arteries  were  observed  moderate  in  size  and  Aurying  in  calibre  at  a time  when  the  heart 
was  acting  well.  Hence  it  was  eHdeiit  that  the  middle  portions  of  the  cord  are  not 
* See  “ Preliminary  Account,  &c.,”  before  referred  to. 
t In  the  original  manuscript  I was  obliged  to  express  my  regret  that  time  bad  not  yet  permitted  me  to 
carry  out  this  idea.  The  dates  in  the  text  indicate  that  it  has  been  done  since  the  paper  was  read. 
