EEGTJLATING  THE  CONTEACTIONS  OF  THE  AETEEIES. 
619 
taken  to  guard  against  warmth  or  dryness,  or  any  other  agency  calculated  to  injure  the 
delicate  tissues  of  the  webs. 
Thus  irregular  contractions,  precisely  similar  to  those  which  accompanied  local  arrest 
of  the  circulation  in  the  experiment  of  October  23rd,  took  place  in  consequence  of 
amputation  of  the  limb ; and  as  there  could  be  no  doubt  that  in  both  cases  they  were 
produced  in  the  same  manner,  there  was  no  longer  any  reason  to  suspect  that  sympa- 
thetic ganglia  in  the  trunk  might  have  had  any  share  in  their  development  in  the  former 
instance.  Yet  the  circumstance  above  mentioned,  that  in  the  amputated  limb  the  ten- 
dency to  constriction  usually  affected  a considerable  tract  of  the  vessel,  and  sometimes 
its  entire  length,  to  nearly  the  same  degree,  or  in  other  words,  that  the  muscular  fibre- 
cells  of  the  circular  coat  of  the  artery  still  contracted  in  concert  with  each  other,  seemed 
to  imply  the  operation  of  a coordinating  nervous  apparatus  contained  in  the  limb.  It 
appears  probable  that  the  means  by  which  these  concerted  movements  are  induced  are 
nerve-cells  disseminated  through  the  limb,  in  the  same  manner  as  Meissner  has  lately 
shown  to  be  the  case  in  the  mammalian  intestine*.  The  intestines  also  present  a 
parallel  to  the  arteries,  in  the  fact  that  contractions  of  their  unstriped  muscular  fibres 
result  from  arrest  of  the  circulation  in  them;  and  I have  lately  shown f that  these 
movements  are  not  due  to  any  influence  exerted  directly  upon  the  contractile  tissue, 
but  that  the  intestinal  nerves  are  essential  to  their  production.  Thus  we  have  support 
from  analogy  for  the  view  that  the  muscular  contractions  which  occur  under  similar  cir- 
cumstances in  the  arteries  are  induced  by  nervous  agency. 
The  fact  that  the  contraction  produced  in  an  artery  of  the  frog’s  web  by  pressure 
upon  a particular  point  affects  a considerable  extent  of  the  vessel,  instead  of  being 
hmited  to  the  spot  irritated,  is  also  an  argument  for  the  existence  of  a local  coordinating 
apparatus ; for  I find  that  this  occurrence  continues  to  take  place  in  an  amputated 
hmb.  The  observation  was  made  on  the  4th  of  August,  1858.  One  of  the  hind  legs 
of  a frog  having  been  removed  after  a hgature  had  been  passed  round  the  thigh  so  as  to 
prevent  escape  of  the  blood,  pressure  was  made  with  a fine  but  blunt  instrument  over  a 
particular  point  in  the  course  of  a large  artery,  whose  calibre  had  previously  been  accu- 
rately determined  by  micrometer.  The  contractions  which  resulted  affected  the  imme- 
diately adjacent  parts  of  the  vessel  to  an  extreme  degree ; the  effect,  however,  was  not 
limited  to  these,  but  gradually  shaded  off  in  both  directions ; and  even  at  a considerable 
distance,  where  by  ordinary  observation  no  change  might  have  been  detected,  the  micro- 
meter showed  a diminution  from  6°  to  5°;{;,  occurring  immediately  upon  the  u-ritation  and 
subsiding  soon  after.  Similar  results  were  obtained  on  repetition  of  the  experiment. 
* Henle  and  Peetjfee’s  ‘ Zeitschrift,’  2nd  series,  vol.  viii.  1857. 
t Vide  “ Preliminary  Account  of  an  Inquiry  into  the  Functions  of  the  Visceral  Nerves,  &c.,”  Proceedings 
of  the  Eoyal  Society,  vol.  ix.  No.  32.  p.  370. 
f These  degrees  have  a different  value  from  those  mentioned  in  other  parts  of  this  paper,  a different 
micrometer  having  heen  employed. 
