1015 
were  sitiiated  on  the  left  and  at  tlie  top  l)eneatli  the  lines  vvere 
cOunted. 
A nuinber  of  spinal  ganglia  and  pieees  of  the  S[)inal  cord  (fixed 
both  in  Klemming  and  Zenkek  liqnid  and  H.  ini|>regnated)  were 
arranged  in  nnbroken  series  for  iiivestigation  of  the  ligures  of  cell 
divisions  (sectioiis  froin  3 — 5 p in  thickness).  Sonie  spinal  ganglia 
with  dorsal  and  ventral  roots  and  a small  piece  of  the  spinal  cord 
(all  B.  impregnaled)  froin  animals  of  varioiis  ages  were  arranged  in 
nnbroken  series  (longitudinal  sections  of  the  roots  from  5 — 10  p in 
thickness)  for  investigation  as  to  the  occnrence  of  7- and  T^divisions 
and  figures  of  growth  of  the  nerve  tibres. 
The  post-emhryonal  increase  in  the  nnmher  of  the  nerve  /ihres  in 
the  dorsal  and  ventral  roots  of  the  spinal  nerves. 
With  regard  to  the  general  growth  of  whole  animals  from  birth 
to  matnritj  (or  at  least  diiring  the  period  of  active  growth)  works 
have  been  pnblished  on  dallu'!  doniesticns  (Minot ‘),  1908)  Mus  nor- 
roegicus  albinus  (Donai-dson  ^) ),  Lepus  cnnicnlus  (Minot ‘),  1908), 
Cavia  cohaija  (Minot  ^),  1891),  Canis  familiaris  (Aron,  1911* *)), 
Homo  caucas  (Roberts,  1878*)  and  others)  and  Homo  niongol. 
(Mishina,  1904  ’)  ),  eic.  All  those  who  have  stndied  growth  have 
also  acknowledged  and  laid  stress  on  the  need  for  an  analysis 
of  the  total  growth  into  its  components  — the  organs  and  their 
elements  the  cells.  Numerous  investigations  of  the  post-embryonal 
development  of  the  organs  and  even  of  the  cells  have  already 
been  pnblished  by  Donaldson,  Hatai,  Naoki  and  others.  On  the 
other  hand,  as  far  as  I conld  find  from  the  literatnre,  no  in- 
vestigation of  a post-embryonal  growth  of  tlie  nnmber  of  axons  in 
the  nervous  system  seems  so  far  to  have  been  pnblished.  It  is 
certainly  trne  that  there  are  numerous  investigations  on  the  nnmber 
of  nerve  fibres  in  the  dorsal  and  ventral  roots  of  the  spinal  nerves 
and  in  a nnmber  of  cranial  nerves  both  in  full-grown  animals  and 
in  animals  of  different  ages  (especially  M.  norwegicus  albinus),  by 
Dunn,  Hardesty,  Hatai  and  others,  and  in  Homo  by  Stilling, 
Ingbert  and  others,  bnt  they  have  all  been  carried  out  with  the 
help  of  staining  methods  for  mednllary  sheaths  and  so  cannot  afford 
*)  Quoted  from  Donaldson,  H.  H.  An  anatomical  analysis  of  growth.  Trans, 
of  the  5th.  International  Gongress  of  Hygiene  Demography  held  at  Washington 
D.  G.  Sept.  23—28.  1912. 
*)  Donaldson,  H.  H.,  Watson  J.  B.  and  Dunn,  E.  H.  1906.  A comparison  of 
the  white  rat  with  man  in  respect  to  the  growth  of  the  entire  body.  Boas 
Memorial  Volume,  New  York. 
