Anatomie.  — De  Heer  Boeke  biedt  eene  inededeeling  aan  van  den 
Heer  Erik  Agdühr  : “is  the  post-embryimal  groivth  of  the 
nervous  sijstem  dae  onhj  to  an  increase  in  size  or  a/so  io  an 
mcrease  in  nwnber  of  the  neurones  T' 
(Mede  aangeboden  door  den  Heer  Winkler). 
Introduction. 
While  investigating  the  effect  of-  training  on  the  post-embryonal 
development  of  the  nervons  systein  I was  confronted  with  tlie 
following  probleni.  Is  ihere  generally  an  increase  in  the  nnmber  of 
axons  diiring  the  post-einbryonal  growth  of  the  nervons  systein  ? We 
are  concerned  with  the  roots  of  the  spinal  nerves.  In  the  dorsal  and 
ventral  roots  of  the  spinal  nerves  there  is,  as  is  shown  in  more 
detail  below,  no  7-  and  J^-division  of  the  nerve  fibres.  Tlie  problem 
is  thus  practically  identical  with  another,  viz. : Is  (here  an  increase 
in  the  number  of  nenrones  diiring  the  post-einbryonal  development? 
Up  to  the  present  time  the  condition  of  this  question  has  been 
siich  that  the  [lossibility  referred  to  has  been  regarded  as  almost 
exclnded.  This  was  due  to  the  snpposition  that  the  nerve-cells  were 
small  bodies  so  miich  differentiated  that  divisions  in  them  coiild  not 
be  imagined.  Figures  of  division  of  cells  in  the  central  nervoiis 
System  of  animals  only  a few  days  old  have,  however,  been  described, 
although  very  eminent  investigators,  snch  as  Marinesco,  Phenant, 
Vai-enza,  etc.  deny  that  these  fignres  have  anything  to  do  with  the 
nerve  elements,  bnt  consider  them  to  be  stroma  elements.  Dnring 
recent  years  the  literature  points  to  some  extent  in  the  direction  of 
the  possibility  of  a [)OSt-embryonal  new  forrnation  of  nenrones  taking 
place  — althongh  the  newly-formed  nenrones  are  only  considered 
as  replacing  those  that  have  been  destroyed  by  degeneration. 
The  resnlts  of  the  investigation  nndertaken  by  me  with  regard 
to  training  (exercising)  were  of  snch  a nature  as  to  be  difticnlt  of 
explanation  in  the  absence  of  a real  increase  in  the  number  of 
neurones  dnring  the  post-embryonal  growih  of  the  animal.  1 was 
b So  far  only  a preliminary  communication  has  been  published : Der  Einfluss 
der  Trainieren  auf  das  morphologische  Bild  des  motorischen  Nervensystems 
Hygica  1917  (LXXIX). 
