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Wistar  Institnte”  and  other  places.  I too  shall  probablj  pass  on  to 
this  aniinal  if  1 have  occasion  (o  contitiue  the  present  investigations. 
Althoiigh  I was  unaware  of  these  investigations  on  Mus  nonuegicus 
albinus,  I have,  liowever,  amongst  my  inaterial  a species  that  is 
rather  closely  related  to  it,  namely  Mus  rnttus  — a male  and  a 
female  specimen,  and  their  eleven  (11)  young  ones;  of  the  yoiing 
ones,  however,  oidy  three  (10,  20  and  30  days  old  respectively) 
have  been  investigated  up  to  now.  My  material  consists,  in  addition, 
of  58  specimens  of  Mits  inusculus  albinus  (of  ages  rajiging  from 
24  hours  to  over  2 years).  Among  these  58  there  are  several 
litters  — thns,  for  instance,  a male  and  a female,  each  over  two 
years  old,  with  several  generations  of  their  progeny,  42  altogether. 
I had  also  22  specimens  of  Bos  taurus  — (half  of  them  two 
weeks  old  and  the  other  half  over  three  years  — only  n.  trochlearis 
and  n.  oculomotorins  were  investigated),  5 specimens  of  Canis 
familinris,  (the  two  parents  and  three  young  ones  6,  17  and  60 
days  old  respectively),  a number  of  specimens  of  Felis  domestica 
(only  n.  trochlearis  and  n.  occnlomotorius  have  been  investigated 
so  far) *  *).  Among  cold-blooded  animals  there  were  28  toads  {Bufo 
vidgaris)  of  different  lengths,  ranging  from  1,6  to  9,8  cms.  from 
nose  to  tail  — but  the  number  of  those  that  are  near  the  minimum 
and  maximum  dimensions  is  larger  than  those  in  between. 
The  columna  vertebralis  with  its  spinal  cord  and  spinal  nerves 
(even  including  the  spinal  ganglia  of  Bufo,  Mus  musculus  and  Mus 
rattus),  the  central  nerve  System  with  the  attached  sub-dural  parts 
of  the  spinal  and  cranial  nerves  of  (Janis  and  Felis  and  the  sub- 
dural  parts  of  nn.  trochleares  and  oculurnotorii  of  Bos  were  (ixed 
in  a twenty  per  cent  formalin  solution.  Previous  to  this  convenient 
spinal  ganglia  and  pieces  of  the  medulla  spinalis  had  been  taken 
out  for  fixation  in  Flbmming’s  liquid.  The  material  that  had  been 
fixed  in  Flkmming’s  liquid  was  imbedded  in  paraffin  and  was  partly 
cut  into  sections  3 — 5 g thick,  which  were  stained  with  the  ii-on- 
alum-hematoxylin  of  Heidenhain  and  eosin.  The  mateilal  that  had 
been  fixed  in  formalin  was  impregnated  in  pieces  according  to  my 
modificatiofts  ’)  of  Bifj,scho\vsky’s  method  of  silver  irnpregnation, 
b I shall  give  a more  detailed  account  of  these  matters  in  a subsequent  and 
more  extensive  publication. 
*)  Agduhr,  Eeik,  Ueber  Stückfarbung  mit  Bielschowsky’s  Silberimpragnations- 
methode.  Einige  Modifikationen.  Zeitschr.  f.  wiss.  Mikrosk.  u.  f.  mikr.  Techn. 
Bd.  34.  1917. 
