ME.  J.  LISTEE  ON  THE  EAELY  STAGES  OF  INFLAMMATION. 
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for  an  hour  or  more : also  its  effects  appeared  inconsistent  with  my  theory ; for  while 
it  ultimately  gave  rise  to  diffusion  of  the  pigment  to  even  a greater  extent  than  I 
had  seen  occur  with  mustard,  yet  it  induced  only  comparatively  slight  appearances  of 
congestion.  Chloroform  also  seemed  at  first  still  more  anomalous  in  its  operation, 
though  in  the  opposite  way ; for  though  it  was  pre-eminently  potent  in  inducing  con- 
gestion, it  caused  no  alteration  whatever  in  the  appearance  of  the  pigment,  whether 
mildly  or  strongly  applied. 
Afterwards,  as  the  true  nature  of  the  pigmentary  functions  became  unveiled,  and 
further  facts  were  developed,  these  difficulties  were  completely  cleared  away.  The  first 
step  towards  their  solution  was  made  in  an  experiment  with  ammonia.  A frog  being 
placed  under  chloroform,  I covered  the  whole  of  the  foot  with  sweet  oil,  except  a small 
area  in  one  of  the  webs,  the  pigment  being  in  the  stellate  condition,  ^.  e.  about  midway 
between  perfect  concentration  and  full  diffusion.  An  assistant  then  held  at  a short 
distance  above  it  a piece  of  lint  soaked  in  the  strongest  liquor  ammonise,  so  that  its 
pungent  alkaline  vapour  might  play  upon  the  exposed  area,  while  the  rest  of  the  foot 
was  protected  by  the  oil.  This  having  been  continued  for  a few  seconds,  accumulation 
of  corpuscles  and  stagnation  occruTed  in  the  vessels  of  the  area,  without  any  change 
in  the  appearance  of  the  pigment.  After  a while,  however,  the  creature  happened  to 
grow  pale,  and,  in  the  web  generally,  the  pigment  became  completely  concentrated  so  as 
to  assume  the  dotted  aspect,  but  in  the  part  which  was  the  seat  of  congestion  it  remained 
stellate  as  before.  Hence  it  appeared  that  though  the  ammonia  did  not  cause  any 
change  in  the  distribution  of  the  pigment,  it  had  in  reality  produced  a great  effect  upon 
the  chromatophorous  cells,  which,  in  the  area  exposed  to  its  infiuence,  had  been  deprived 
of  the  power  of  concentration  by  the  mildest  degree  of  action  of  the  alkali  that  sufficed 
to  induce  stagnation  of  the  blood.  On  examination  of  the  web  about  four  hours  later, 
resolution  of  the  stagnation  was  found  to  have  taken  place,  though  there  was  still  some 
excess  of  corpuscles,  with  marked  adhesiveness  of  the  colourless  ones  in  the  vessels  of 
the  ammonia  area.  The  creature  was  now  released  for  the  night.  Next  morning  the 
integument  was  in  the  opposite  extreme  of  colour,  being  almost  black,  and  the  pigment 
had  the  reticular  appearance,  being  fully  diffused  throughout  the  whole  web,  except  the 
central  part  of  the  ammonia  area,  where  it  retained  the  same  stellate  condition  as  the 
day  before.  Hence  it  appeared  probable  that  the  difiusive  power,  as  well  as  the  con- 
centrating, had  been  paralysed  by  the  ammonia,  but  had  been  recovered  in  all  the  area 
except  the  part  that  was  likely  to  be  the  last  to  regain  its  functions.  To  ascertain 
whether  the  concentrating  power  had  also  been  regained,  I killed  the  frog  and  ampu- 
tated the  leg ; soon  after  which  the  usual  'post  morteim  concentration  took  place  com- 
pletely in  the  web  generally,  while  in  the  central  part  of  the  area  the  medium  state  was 
still  retained,  and  in  the  rest  of  its  extent  concentration  considerably  beyond  the  medium 
state,  but  short  of  the  full  degree,  supervened,  showing  that  recovery  of  function  had 
taken  place  to  a considerable  extent,  but  was  not  yet  quite  complete. 
I now  felt  little  doubt  that  chloroform  also  possessed  the  power  of  arresting  the  pig- 
mentary functions ; but  in  order  to  prove  the  fact  I killed  a dark  frog,  and  placed  one 
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