ME.  J.  LISTEE  ON  THE  EAELT  STAGES  OE  INELAMMATION. 
687 
atmosphere.  With  a view  to  ascertaining  whether  the  congestion  was  due  to  the  direct 
action  of  the  acid  upon  the  tissues,  I made  the  following  experiment.  Having  killed  a 
dark  frog  and  amputated  both  legs,  and  ascertained  by  microscopic  examination  that 
the  pigment  was  fully  diffused  in  the  webs,  I put  one  limb  into  a bottle  of  “ aerated 
water”  and  the  other  into  ordinary  water : the  latter  soon  became  pale  through  post 
mortem  concentration,  but  the  former  remained  as  dark  as  ever  during  the  two  hours  for 
which  it  was  retained  in  the  solution  of  carbonic  acid,  the  direct  action  of  which  upon 
the  bloodless  tissues  was  thus  demonstrated.  An  hour  after  the  limb  had  been  taken 
out,  however,  it  was  evidently  recovering,  being  distinctly  lighter  in  colour  than  it  had 
been,  and  two  hours  later  it  was  quite  pale,  and  the  pigment  in  the  webs  was  found  to  be 
in  almost  the  extreme  degree  of  concentration.  In  subsequent  similar  experiments  I left 
the  leg  in  the  aerated  water  for  a longer  time,  during  which  it  always  retained  precisely 
the  same  tint  that  it  had  when  first  introduced ; and,  if  left  for  many  hours,  showed 
signs  of  loss  of  vitality,  by  the  early  supervention  of  cadaveric  rigidity  and  exfoliation 
of  the  epidermis ; but  if  it  was  taken  out  within  about  four  hours,  the  pigment-cells 
recovered  completely ; and  in  one  case  a leg  not  removed  for  nine  hours  regained,  never- 
theless, to  a considerable  extent,  the  faculty  of  concentration*.  Thus  it  appears  that 
cai’bonic  acid,  though  exercising  a powerful  sedative  influence  upon  the  tissues,  and 
paralysing  for  the  time  their  vital  energies,  so  as  to  give  rise  to  intense  inflammatory 
congestion,  yet,  even  after  a very  protracted  action,  leaves  them  in  a state  susceptible 
of  speedy  recovery. 
Here  we  see  for  the  first  time  a satisfactory  solution  of  the  much-debated  problem  of 
the  cause  of  congestion  of  the  lungs  in  Asphyxia ; for  there  can,  I conceive,  be  no  doubt 
that  the  prdmonary  tissues,  exposed  under  ordinary  circumstances  to  the  influence  of  a 
free  supply  of  oxygen,  suffer,  like  those  of  the  frog’s  web,  from  the  vicinity  of  an 
abnormal  proportion  of  carbonic  acid,  and  inflammatory  congestion  is  the  necessary 
consequence.  At  the  same  time,  the  rapid  recovery  of  the  lungs  from  asphyxial  con- 
gestion of  considerable  duration,  when  the  normal  atmosphere  is  readmitted,  finds  an 
equally  close  parallel  in  the  speedy  return  both  of  the  pigment-cells  and  the  blood  to 
the  healthy  condition  when  the  foot  of  the  frog  is  removed  from  the  aerated  water. 
But  the  most  important  lesson  to  be  learnt  from  these  simple  experiments  with  car- 
bonic acid  upon  amputated  hmbs,  is  that  the  tissues  possess,  independently  of  the  cen- 
tral organs  of  the  nerv^ous  system,  or  of  the  circulation,  or  even  of  the  presence  of  blcjiod 
within  the  vessels,  an  intrinsic  power  of  recovery  from  irritation,  when  it  has  not  b6en 
carried  beyond  a certain  point ; a principle  of  fundamental  importance,  which  has  never 
before,  so  far  as  I am  aware,  been  established  or  conjectured.  It  applies  equally  in  the 
case  of  other  irritants.  Thus  having  transmitted  for  about  a quarter  of  a minute, 
through  one  of  the  webs  of  a dark  amputated  limb,  powerful  galvanic  currents,  such  as 
I had  before  ascertained  to  cause  stagnation  of  the  blood  when  operating  for  an  instant 
upon  the  living  animal,  I found,  after  the  lapse  of  an  hour  and  a quarter,  that  the  pro- 
* This  observation  was  made  subsequently  to  the  reading  of  the  paper. 
MDCCCLVIII.  4 X 
