686 
MR.  J.  LISTER  ON  THE  EARLY  STAGES  OF  IXFLAADIATION. 
The  same  thing  was  afterwards*  seen  in  a case  in  which  a small  drop  of  wood-vinegar 
was  placed  upon  one  of  the  webs  of  a frog  which  had  been  deprived  of  the  power  of 
voluntarily  moving  the  limbs  by  passing  a knife  between  the  occiput  and  the  atlas,  so  as 
to  sever  the  brain  from  the  cord.  The  fluid  being  thus  allowed  to  lie  quite  undisturbed, 
did  not  spread  at  all  upon  the  web,  which  was  dry  before  it  was  applied.  It  produced 
its  effects  very  slowly,  so  that,  after  the  lapse  of  three  and  a half  hours,  the  blood  in  the 
area  covered  by  it,  while  everywhere  presenting  inflammatory  appearances,  was  still  only 
partially  stagnant.  Yet  throughout  this  space  the.  pigment  retained  exactly  the  same 
moderate  degree  of  diflusion  as  it  had  at  the  beginning  of  the  experiment,  although  in 
the  interval  complete  concentration  had  taken  place  elsewhere ; and  a very  striking  con- 
trast was  presented  between  the  stellate  pigment  with  the  adhesive  though  still  moving 
blood-corpuscles  where  the  web  was  wet  with  the  vinegar,  and  the  dotted  pigment  and 
perfectly  healthy  circulation  in  the  dry  parts  immediately  adjacent. 
Seeing,  then,  that  complete  suspension  of  the  pigmentary  functions  may  be  caused  by 
an  amount  of  irritation  which  induces  only  a minor  degree  of  congestion,  and  further, 
that  (as  we  learn  from  the  experiment  with  chloroform  vapour)  a still  milder  operation 
of  an  u'ritant  renders  these  functions  sluggish  though  not  completely  arresting  them,  we 
seem  to  have  sufficient  evidence  that  impairment  of  the  functional  activity  of  the  chro- 
matophorous  cells  occurs  in  the  very  earliest  stages  of  that  primary  change  in  the  tissues 
which  leads  to  inflammatory  derangement  of  the  blood. 
It  was  seen  in  the  ammonia  experiment  related  above,  that  resolution  having  taken 
place  in  the  congested  area,  the  pigment-cells  of  the  part  recovered  the  faculty  both  of 
diflusion  and  concentration.  This  might  have  been  pretty  confidently  predicted;  for 
as  congestion  is  a necessary  consequence  of  the  disorder  produced  in  the  tissues  by  mi- 
tants,  we  might  have  been  almost  sure  that  the  return  of  the  ^ital  fluid  to  that  healthy 
condition  in  which  it  is  flt  for  free  transmission  through  the  vessels,  must  be  pre- 
ceded by  a restoration  of  the  living  solids  to  their  normal  state.  In  the  case  alluded  to. 
however,  no  sign  of  recovery  of  the  pigment-cells  appeared  till  after  the  circulation  had 
become  re-established ; and  even  when  several  hours  had  elapsed,  they  still  remained 
paralysed  in  the  central  part  of  the  area  on  which  the  ammonia  had  acted.  This  is  in 
harmony  with  the  fact  lately  pointed  out,  that  complete  suspension  of  the  pigmentary 
functions  may  accompany  a state  of  the  blood  short  of  actual  stagnation ; and  both 
appear  to  depend  upon  the  circumstance  that  the  chromatophorous  cells  are  an  ex- 
tremely delicate  form  of  tissue. 
The  rate  of  recovery  of  the  pigment-cells  varies  greatly,  however,  in  different  cases, 
and  in  this  respect  much  depends  upon  the  nature  of  the  irritant.  An  example  of  an 
agent  of  this  class  producing  only  very  transient  effects  on  the  pigmentary  functions  is 
presented  by  carbonic  acid.  It  has  been  before  mentioned  that  the  immersion  of  a 
living  frog  for  about  a quarter  of  an  hour  in  water  highly  charged  %vith  that  gas,  gives 
rise  to  complete  stagnation  of  the  blood  in  the  webs,  although  the  heart  still  continues 
beating,  but  that  resolution  occurs  after  the  animal  has  been  exposed  for  awhile  to  the 
* This  experiment  was  performed  subsequently  to  the  reading  of  the  paper. 
