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XXX.  On  the  Cutaneous  Pigmentary  System  of  the  Frog.  By  Joseph  Lister,  Esq., 
F.R.C.S.  Eng.  and  Edin.,  Assistant  Surgeon  to  the  Royal  Infirmary,  Edinburgh, 
Communicated  by  J)r.  Sharpey,  Sec.  R.S. 
Eeceived  June  18, — Eead  June  18,  1857*. 
The  fact  that  the  skin  of  the  frog  is  capable  of  varying  in  colour,  has  been  for  some 
years  known  to  German  naturalists.  The  first  account  of  the  mechanism  by  which  these 
changes  are  effected,  appears  to  have  been  given  by  Professor  Brucke,  of  Vienna,  in 
1852f,  and  the  subject  has  since  been  very  carefully  investigated  by  Dr.  yon  Wittich 
of  KonigsbergJ,  and  Dr.  E.  HxIRLess  of  Munich  §.  All  these  observers  describe  the 
dark  pigment  as  contained  in  stellate  cells,  each  composed  of  a central  part  or  body  and 
several  tubular  ofisets,  which,  subdividing  minutely  and  anastomosing  freely  with  one 
another  and  also  with  those  of  neighbouring  cells,  constitute  a delicate  network  in  the 
substance  of  the  true  skin.  They  describe  the  dark  contents  as  sometimes  concentrated 
in  the  bodies  of  the  cells,  at  other  times  diffused  throughout  the  branching  processes, 
the  skin  of  the  creature  being  pale  in  the  former  case  and  dark  in  the  latter.  In  the 
tree-frog  the  change  from  a dark  to  a pale  state  of  the  body  generally  was  induced  by 
bringing  the  creature  into  a bright  light,  by  psychical  excitement  (as  was  supposed^), 
or  by  galvanizing  the  spinal  cord;  and  a similar  effect  was  produced  on  a particular 
portion  of  the  surface  by  irritating  it  mechanically,  or  with  oil  of  turpentine,  or  by 
galvanism  apphed  either  dhectly  to  the  part,  or  through  branches  of  nerves  leading  to 
it.  After  the  source  of  irritation  was  removed,  the  skin  returned  somewhat  slowly  to 
its  former  colour;  and  von  Wittich  noticed  that  when  the  paleness  produced  by  dhect 
irritation  had  passed  off,  the  tint  became  deeper  in  the  irritated  spot  than  elsewhere. 
The  esculent  frog  exhibited  similar  phenomena,  but  was  less  sensitive.  The  concen- 
trated state  of  the  pigment  is  attributed  by  all  the  observers  above  named  to  contraction 
of  the  cells,  while  the  diffused  condition  is  supposed  due  to  their  relaxation.  The  con- 
* During  the  time  that  has  elapsed  between  the  reading  of  this  paper  and  its  publication,  several  new 
observations  have  been  made,  which  it  has  been  thought  best  to  introduce  into  the  text,  distinguished  by 
date  or  foot-note  from  the  matter  of  the  original  manuscript. 
t Dntersuchungen  iiber  den  Farbenwechsel  des  Africanischen  Chamaeleons,  iv.  Band  der  mathemat. 
naturwissenshaftl.  Classe  der  Eiaiserl.  Acad.  d.  Wissensclift.  Wien.  This  paper  I have  not  yet  had  an  oppor- 
tunity of  consulting. 
+ Mullee’s  Archiv,  1854. 
§ Zeitschrift  fvir  Wissenschaftliche  Zoologie,  vol.  v.  1854. 
IT  This  rests  on  the  authority  of  von  Wittich;  but,  for  anything  stated  to  the  contrary  in  his  paper, 
the  effects  ascribed  to  psychical  excitement  may  have  been  connected  with  the  efforts  of  the  creature  in 
struggling,  independently  of  any  emotional  change. 
