EEGULATING-  THE  CONTEACTIONS  OF  THE  aETERIES. 
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essential  to  the  regulation  of  the  arterial  contractions  in  the  feet.  The  following- 
experiment  confirmed  this  important  conclusion,  and  also  furnished  additional  informa- 
tion. 
On  the  20th  of  October,  a large  frog  having  been  placed  under  chloroform,  the  cord 
was  divided  transversely  at  the  distance  of  about  one-fifth  of  its  length  from  the  posterior 
extremity.  At  4^  20“  p.m.,  just  after  the  operation,  an  artery  in  the  right  foot  measured 
2^°,  the  vessels  appearing  generally  of  pretty  full  size,  and  the  flow  of  blood  rapid  through 
the  web.  At  4^  25“  the  cord  was  again  cut  across  a little  behind  the  mid-scapulee,  at  a 
distance  from  the  occiput  of  somewhat  more  than  a quarter  of  the  length  of  the  cord. 
At  4^  33“  the  diameter  of  the  vessel  was  At  4^  40“  the  portion  of  cord  included 
between  the  incisions  was  removed,  without  any  interference  with  either  the  anterior  or 
posterior  segment.  It  was  observed  that  a large  branch  for  the  hind  legs,  furnished  by 
the  middle  segment,  had  to  be  divided  during  its  removal,  and  immediately  after  the 
operation  the  artery  measured  2^°,  and  the  flow  of  blood  in  the  web  was  much  more 
rapid  than  before.  At  4*^  45“  the  artery  had  contracted  to  2°,  at  5^  7“  it  measured  short 
of  2°,  and  a minute  later  was  again  2°.  At  5*'  11“  I introduced  a fine  needle  into  the 
anterior  segment  of  the  cord  with  the  effect  of  causing  convulsive  movements  of  the  fore 
legs,  but  no  change  whatever  in  the  cahbre  of  the  artery  in  the  hind  leg.  I afterwards 
repeated  this  experiment  twice,  and  the  last  time  carried  the  needle  on  into  the  brain, 
and  stirred  it  up  thoroughly,  but  no  effect  was  produced  upon  the  vessel.  At  5’’  23“ 
the  whole  brain  was  removed,  together  with  the  anterior  segment  of  the  cord ; the  artery, 
however,  still  continued  to  measure  2°.  At  this  time  the  circulation,  though  somewhat 
enfeebled,  was  stdl  pretty  good.  At  5'’  53“  a complicated  operation  was  performed 
upon  the  left  thigh,  to  which  I need  not  allude  further  than  to  mention,  that  it  no 
doubt  involved  exposure  of  the  other  foot  to  a higher  temperature  than  before,  in  con- 
sequence of  the  ricinity  of  my  hands,  and  this  was  probably  the  cause  of  the  dilatation 
of  the  arteries  observed  immediately  afterwards,  that  which  had  been  previously  measured 
being  now  2f°.  Five  hours  later  the  artery  was  again  2°,  but  the  heart’s  action  was 
excessively  languid.  Next  morning  the  circulation  was  going  on  steadily,  though  some- 
what slowly,  the  heart  having  obviously  recovered  to  some  extent  during  the  night. 
The  arteries  were  larger  than  ever  seen  before ; the  calibre  of  that  above  noted  being  3^, 
and  there  were  a good  many  blood-corpuscles  adliering  to  the  walls  of  the  vessels.  It 
is  probable  that  the  small  posterior  segment  of  the  cord  had  become  impaired  in  its 
powers,  but  that  it  was  still  acting  to  some  extent  was  evident  from  the  circumstance 
that  after  its  removal  at  10*'  56“  a.m.,  the  vessel  was  found  increased  to  4°,  and  in  con- 
sequence of  the  arterial  dilatation,  the  stagnation  of  the  red  corpuscles,  which  existed  in 
several  parts  of  the  webs,  was  almost  entirely  dispelled,  although  the  action  of  the  heart 
did  not  appear  to  have  been  changed.  During  the  next  half-hour  the  artery  was 
measured  four  times,  and  was  in  every  instance  found  to  be  still  4°  in  diameter.  I may 
mention  that  I measured  the  posterior  segment  of  the  cord  immediately  after  its  removal, 
and  found  its  length  to  be  one-sixth  of  that  of  the  whole  cord ; it  was  in  fact  little  more 
