666 
ME.  J.  LISTEE  OjS^  THE  EAELT  STAGES  OF  I^'FLA:^DIATIO^^. 
powerfully  to  distend  them  with  blood,  but  not  otherwise.  Eecent  physiological  dis- 
covery has  shown  that  the  arteries  are  not  singular  in  being  thrown  into  a state  of 
muscular  relaxation  through  irritation  of  the  parts  of  the  nervous  system  connected 
with  them,  the  same  being  the  case  with  the  heart,  the  intestines,  and  appai’ently  also 
with  other  hollow  viscera.  In  a preliminary  account  of  an  inquuy  into  the  functions 
of  the  visceral  nerves,  pubhshed  in  the  ‘ Proceedings  ’ of  this  Society*,  I have  given  some 
notice  of  experiments  which  seem  to  show  that  in  the  case  of  the  viscera  alluded  to,  the 
state  of  relaxation  under  such  circumstances  is  the  result  of  the  more  energetic  opera- 
tion of  nerves,  which,  when  working  more  mildly,  increase  the  muscular  action  of  the 
‘ same  organs ; the  functions  of  the  ganglia  specially  concerned  in  regulating  the  move- 
ments of  the  viscera  being  exalted  by  gentle  stimulation  on  the  part  of  the  afferent 
nerves  connected  with  them,  but  depressed  by  stronger  excitation.  In  that  paper  the 
opinion  was  expressed,  that  the  same  explanation  probably  applies  to  the  relaxation  of 
the  arteries,  in  consequence  of  nervous  hritation ; the  general  impression  conveyed  by 
the  experiments  with  warm  water  above  related  being  that  arterial  contraction  was  most 
apt  to  show  itself  when  the  degree  of  irritation  was  least,  while  dilatation  was  most 
marked  when  the  stimulus  was  strongest.  I have  lately  seen  a striking  illustration  of 
this  principle  in  a very  simple  experiment,  which  I was  mduced  to  make  in  consequence 
of  reading  a paper  recently  published  by  a French  author,  M.  J.  ]\LiEETf.  If  a blunt- 
pointed  instrument,  such  as  the  end  of  a pair  of  dissecting  forceps,  is  drawn  with  gentle 
pressure  along  the  back  of  the  hand  while  it  is  in  a state  of  moderate  redness,  the  blood 
being  driven  out  of  the  vessels,  a pale  streak  results,  which  immediately  disappears,  in 
consequence  of  the  return  offhe  blood  into  the  part.  In  a few  seconds,  however,  a pale 
stripe,  towards  a quarter  of  an  inch  in  breadth,  becomes  developed  at  each  side  of  the 
line  along  which  the  instrument  passed,  that  line  having  now  assumed  a red  coloiu-,  if 
the  pressure  employed  was  at  all  forcible.  This  is  M.  Maeet’s  experiment ; and  there 
can  be  net  doubt  that  his  interpretation  of  the  secondary  paleness  is  correct,  "siz.  that  it 
depends  on  reflex  arterial  contraction.  The  red  line,  when  it  occurs,  is  endently  due  to 
the  direct  action  of  the  pressure  upon  the  tissues,  being,  as  M.  ISLiket  correctly  states, 
exactly  of  the  same  breadth  as  the  instrument  used.  But  I find  that  if  the  pressm-e  be 
made  with  considerably  greater  force,  so  as  to  be  positively  pamful,  while  the  fii'st  white 
streak  appears  as  before  in  consequence  of  the  blood  being  dispelled  from  the  vessels, 
the  secondary  paleness  does  not  occur,  but,  on  the  contrary,  a patch  of  the  adjacent  skin, 
extending  for  perhaps  half  an  inch  on  each  side,  assumes  abnormal  redness,  which  lasts 
for  a longer  time  than  the  paleness  to  which  the  other  experiment  gh'es  rise.  Here, 
the  irritation  being  severe,  the  blood  vessels  are  throum  through  the  mediimi  of  the 
* Vol.  ix.  No.  32.  The  paper  here  referred  to  was  written  subsequently  to  the  reading  of  the  manu- 
script of  this  essay,  and  this  was  also  the  case  with  the  remarks  in  the  text  on  determination  of  blood. 
•f  ‘ Eecherches  Hydrauliques  sur  la  Circulation  du  Sang,’  par  M.  J.  Mauet.  The  sepai’ate  copy  of  this 
paper,  sent  me  by  the  author,  does  not  contain  any  mention  of  the  Journal  in  which  it  was  published,  so  that 
I am  unable  to  give  proper  reference  to  it. 
