le/irffi.  Ernst.  Briickef  has  added  observations  to  those  which  he  published
ar,  to  prove  that  the  oflice  of  the  tapetum  is  to  reflect  light,  on  the  stalT-
I  bodies  of  that  part  of  the  retina  which  is  most  used  in  vision,  and  so  to
rision  possible  to  certain  animals,  at  times  when  those  without  a  tapetum
I  darkness.  He  has  produced  an  extensive  comparative  anatomv  of  the
m ;  and  has  shown  that  while  all  the  other  various  colours  which  the  tape-
^the  dog  and  other  animals  presents  in  different  lights  depend  on  it  alone,
i  colour  which  it  occasionally  reflects  is  due  to  the  laree  vessels  beneath  it
X  into  view.  And  he  has  discovered  that  there  are  m  different  animals
itinct  kinds  of  tapetum, — the  one  fibrous,  the  other  cellular.  The  fibrous
a,  which  has  been  long  known  to  consist  of  smooth,  transparent,  uudulat-
Nres,  is  found  in  ruminants,  solidungula,  the  elephant,  some  marsupials,
I  whale  tribe.  The  cellular  tapetum,  hitherto  unknown,  is  found  in  the
m  and  in  seals.  The  cells,  which  may  be  best  seen  after  pieces  of  tape-
ve  been  macerated  for  a  day  or  two  in  water  with  some  hydrochloric  acid
bol,  are  smooth,  nucleated,  elongated,  unequally  and  imperfectly  hexa-
and  very  large,  measuring  from  *000d  to  *0028  of  an  inch  in  cfiameter.
«Mich.  zur  Kennt.  dct  kornignn  Pigmend  <ler  Wirbelthiere;  Zurich,  1844,  4to,  p.  6.
ofi  ArchiT,  1845,  Heft  iv,  p.  387.
286


Mb.  Pagct's  Report  on  the  Progrem  of


Whh  tnnsmitted  light  thej  >ppcv  yellowish,  and  their  nodei  pdlodd ;  \
reflected  light,  ther  are  beaotifiillj  blae  and  their  nuclei  blacL    Thej
liarly  subject  to  deposits  of  earth j  matter.
