ME.  J.  LISTEE  ON  THE  EAELT  STAGES  OF  INFLAMMATION. 
655 
see,  require  a veiy  different  interpretation.  It  has  also  been  based  upon  a supposed 
analogy  between  the  circulation  of  the  blood  in  the  higher  animals  and  certain  move- 
ments observed  to  occur  without  any  visible  source  of  mechanical  power  in  tubes  and 
cells  in  the  vegetable  kingdom,  and,  as  was  thought,  also  in  some  of  the  lower  forms  of 
animal  life : but  though  a resemblance  may  probably  exist  between  some  of  these  and 
the  movements  occurring  m the  processes  of  secretion  and  absorption  and  the  circula- 
tion of  nutrient  fluid  among  the  tissues  of  intercapillary  spaces  and  non-vascular  parts, 
the  progress  of  modern  discovery  tends  to  show  that  the  comparison  is  altogether  inap- 
plicable to  the  sanguiniferous  system.  It  would,  I think,  be  out  of  place  to  enter  fully 
into  this  discussion  on  the  present  occasion,  but  my  own  experience  with  the  frog  leaves 
no  doubt  in  my  mind  that  in  that  animal  contractions  of  the  heart  are  the  only  cause  of 
the  circulation.  I will  content  myself  with  mentioning  two  observations  bearing  upon 
this  question.  The  first  of  these  has  reference  to  certain  movements  which  occur  for  a 
considerable  time  after  cessation  of  the  heart’s  action,  and  which,  though  of  trivial  and 
uncertain  character,  have  had  much  stress  laid  upon  them  in  this  discussion.  I have 
ascertained  by  observations  made  in  several  different  cases,  that  they  are  produced  by 
occasional  spontaneous  contractions  and  relaxations  of  the  arteries.  These  changes  in 
the  calibre  of  the  vessels  continue,  even  in  an  amputated  limb,  for  days  after  severance 
from  the  body*:  I have  repeatedly  watched  them  taking  place,  and  seen  them  give  rise 
to  the  movement  of  the  blood. 
The  other  fact  to  which  I will  allude,  appears  to  me  to  decide  of  itself  the  question  at 
issue.  IIa\dng  occasion  to  examine,  under  chloroform,  some  very  small  frogs,  measuring 
about  an  inch  from  the  tip  of  the  nose  to  the  end  of  the  coccyx,  I found  that  the  blood 
in  the  capillaries  invariably  flowed  in  a stream  pulsating  synchronously  with  the  beats 
of  the  heart,  which  were  \isible  through  the  parietes  of  the  thorax ; and  however  mildly 
the  anaesthetic  was  administered,  the  motion  was  commonly  exceedingly  slight  between 
the  pulses.  Not  unfi-equently,  although  the  arteries  remained  of  full  size,  the  blood 
moved  in  jerks,  with  considerable  intervals  of  absolute  stillness  between  the  successive 
impulses  which  the  contractions  of  the  heart  occasioned ; yet  no  accumulation  of  cor- 
puscles was  produced  in  the  capillaries,  however  long  the  animal  was  kept  under  obser- 
vation. Had  any  other  cause  of  motion  than  the  action  of  the  heart  operated  upon  the 
blood,  there  must  have  been  a continuous  flow,  however  much  accelerated  at  each  pulse  ; 
for  I must  add,  that  there  was  nothing  whatever  of  recoil  after  each  onward  movement, 
nor  anything  indicating  obstruction  to  the  progress  of  the  blood. 
Thus  in  these  cases  of  intermitting  capillary  flow,  it  was  matter  of  direct  observation 
that  the  heart  was  the  sole  cause  of  the  blood’s  motion ; and  as  we  know  that  in  an 
animal  under  the  influence  of  chloroform  the  changes  of  the  blood  from  arterial  to 
venous,  and  vice  versd,  continue  to  occur  in  the  .systemic  and  pulmonary  capillaries,  and 
as  we  have  every  reason  to  believe  that  the  processes  of  nutrition  in  the  different  parts 
* See  the  preceding  paper  on  the  parts  of  the  Nervous  System  which  regulate  the  contractions  of  the 
arteries,  p.  618. 
MDCCCLVIII.  4 R 
