672 
ME.  J.  LISTEE  Oy  THE  EAELT  STAGES  OF  IXFLA^JAIATIOy. 
ing  to  aggregate  into  rouleaux,  and  giving  a lumpy  aspect  to  the  somewhat  dark  streams 
in  the  larger  vessels : but  turning  to  another  place,  I found  the  blood  there  of  pale  tint 
and  perfectly  homogeneous  aspect ; nor  could  I detect  by  a careful  search  any  evidence 
of  a tendency  on  the  part  of  the  -white  corpuscles  to  stick  to  the  vascular  parietes.  It 
happened  that  there  was  complete  absence  of  flow  in  one  artery  and  concomitant  vein  of 
considerable  size,  yet  not  a rouleau  was  to  be  seen  either  in  them  or  in  any  of  their 
branches.  On  the  contrary,  the  red  discs  lay  at  about  equal  distances  from  each  other, 
uniformly  distributed  throughout  the  cahbre  of  the  vessels;  and  this  state  of  things 
remained  unchanged  during  about  a quarter  of  an  hour,  in  which  I continued  to  obseiTe 
them  in  their  perfectly  quiescent  condition.  On  examination  of  some  blood  fi-om  the 
heart  of  this  bat  shortly  after,  the  red  corpuscles  exhibited  a very  remarkable  degree  of 
adhesiveness,  such  as  I had  never  seen  in  human  blood*,  presenting  a glaring  conti-ast 
with  their  state  within  the  vessels f. 
Thus  we  may,  I think,  regard  it  as  fully  established,  that,  in  mammaha  as  well  as  in 
amphibia,  both  the  red  discs  and  the  colourless  globules  of  the  blood  are  completely 
free  from  adhesiveness  within  the  vessels  of  a perfectly  healthy  part,  but  that  when  the 
tissues  have  suffered  from  irritation,  both  kinds  of  corpuscles  assume,  in  proportion  to  the 
severity  of  the  affection,  a degree  of  that  tendency  to  stick  to  one  another  and  to  neigh- 
bouring objects  which  they  possess  when  -withdrawn  from  the  body,  and  consequently 
experience  obstruction  to  their  progress  through  the  minute  vessels. 
And  here  I cannot  avoid  remarking,  that  this  principle  explains,  if  it  does  not  alto- 
gether reconcile,  the  discordant  opinions  of  physiologists  regarding  the  causes  of  the 
cu’culation.  It  shows  that  while  there  is,  as  we  have  before  seen  J,  strong  ground  for 
agreeing  with  those  who  hold  that  the  flow  of  the  blood  is  due  simply  to  the  contrac- 
tions of  the  heart,  aided,  in  animals  with  valved  veins,  by  the  actions  of  the  muscles,  the 
resphatory  movements,  and,  in  the  case  of  the  bat’s  Aving,  by  rhythmical  venous  con- 
tractions ; yet  there  is  also  much  truth  in  the  -view  of  those  who  maintahi  that  the  tissues 
of  a part,  independently  of  any  change  of  calibre  in  the  vessels,  exercise  a great  influence 
upon  the  progress  of  the  blood  through  the  capillaries.  For  though  the  tissues  do  not. 
as  has  been  hitherto  supposed  by  the  latter  class  of  authorities,  actrfely  promote  the 
circulation,  yet  their  healthy  condition  is  none  the  less  necessary  to  it,  being  essential  to 
the  fitness  of  the  blood  for  transmission  by  the  heart  through  the  minute  A essels. 
* The  remarkable  adhesiveness  of  the  red  corpuscles  of  the  blood  of  this  hat,  ■when  -withdi-awn  from  rhe 
body,  has  been  particularly  described  in  Section  I.,  page  649. 
f Mr.  Whaeton  Jones,  in  the  paper  before  referred  to,  describes  the  red  discs  as  aggregating 
the  vessels  of  the  healthy  bat’s  'wing,  when  their  movement  is  arrested  from  any  cause,  in  the  same  mamicr  as 
in  blood  removed  from  the  body.  Vide  Med.-Chir.  Trans.  Joe.  cit.  I suspect  that  the  pressm-e  of  the  plate  of 
thin  glass  employed  in  order  to  bring  the  necessarily  high  powers  of  the  microscope  to  bear  upon  the  object  is 
apt  to  irritate  the  web  and  give  rise  to  a degree  of  congestion,  characterized  by  a tendency  to  aggregation  ou 
the  part  of  the  red  discs  and  adhesion  of  the  colourless  corpuscles  to  the  walls  of  the  vessels.  I have  observed 
that  results  of  irritation  have  shown  themselves  in  the  web  of  the  frog  when  I have  used  a plate  of  thiu  glass 
in  the  same  manner  as  with  the  bat,  for  the  purpose  of  applying  a liigh  power  to  the  pigmentary  tissue. 
:J:  See  page  654. 
