1046 
botli  glia  and  ganglion  cells.  The  initoses  fomid  _in  the  central 
nervons  sjsteni  of  young  animals  do  not  seem  to  refer  to  so-called 
neiiroblasls  (His)  '),  but  the  preparation  indioates  tliat  Koklliker 
is  right  when,  partly  by  reasoning  and  parfly  by  direct  observations, 
he  cornes  to  the  conclnsion  that  those  “Keiincellen”  that  are  in 
initosis  are  undifFerentiated  epithelinm-cells,  which  give  rise  to  both 
glia  and  ganglion  cells.  Schaper’)  arrivés  at  the  same  result  by  his 
investigations  of  the  course  of  dilFerentiation  in  the  central  nervous 
systeni  of  the  trout.  We  thus  seem  to  be  justified  in  postiilating  as 
a fact  that  as  long  as  tnitoses  can  be  shown  in  the  central 
nervous  System  a new  formation  of  ganglion  cells  is  also  taking  place. 
In  Prenant '*)  we  read  as  follows:  a.  “Les  cellules  nerveuses,  en 
se  différenciant,  out  perdu  Ie  pouvoir  de  se  i-eproduire,  h.  Les  rares 
nuiltiplications  qu’il  a été  possible  d’observer  dans  les  cas  de  cicatri-: 
sation  de  portions  du  névraxe,  appartiennent  a Ia  neuroglie  (Valenza, 
Marinesco,  Monti);  c.  Entin  il  n’est  pas  exclus  que  les  quelques  mitoses 
observées  doivent  également  être  assignées  a la  neuroglie”.  Among 
the  investigators  who  do  not  seem  to  be  able  to  adinit  the  possi- 
bility  of  an  increase  of  the  neurones  during  post-ernbryonic  life  I 
want  to  niention  also  Bizzozero  and  Marinesco  ®).  In  deciding  such 
matter  these  authors  seem  more  or  less  to  have  proceeded  from  the 
idee  prëconcu  that  the  neurons  have  a very  long  life  and 
are  nearly  perpetual.  They  consider  that  this  is  an  absolutely  neces- 
sary  qualiticaiion  if  the  individual  is  to  perserve  its  psychical 
inheritance,  to  form  associations  of  ideas,  and  for  memory  in  general. 
A close  study  of  suitable  preparations  of,  for  instance,  the  spinal 
cord  from  animals  of  different  ages  will  soon  con.vince  us  that 
this  does  not  quite  agree  with  the  real  facts.  For  in  these 
preparations  one  tinds  not  infrequently  figures  of  ganglion  cells 
which  are  degenerating  as  well  as  those  which  indicate  generation. 
Nor  is  the  literature  on  the  subject  without  scattered  statements 
about  observations  of  such  degeneration  in  the  central  nervous 
q His,  Die  Neuroblasten  und  deren  Entslehung  im  embryonalen  Mark.  Arch  f. 
Anal.  u.  Entwickelungsgesch.  1889. 
2)  v.  Koellikeb,  üewebelehre,  Bd.  2,  1893. 
5)  Schaper,  Archiv.  für  Entw.  mech.  der  Organ.  Bd.  5. 
Prenant,  Histologie  et  Anatomie  microscopique,  t.  II,  p.  353,  1911. 
q Bizzozero,  G , Accrescimento  e rigenerazione  nell’organismo  tConferénce  du 
Prof.  G.  Bizzozero  au  Gongrés  international  tenu  a Rome  en  1894).  Voir,  en 
outre,  dans  Ie  2e  volume  des  oeuvres  scientifiques  du  même  auteur  publié  a Milano 
en  1905,  et  dans  les  Arch.  ital  de  Biol.  t.  XXI,  p.  93,  quoted  from  Paladino. 
®)  Marinesco,  G.,  La  celluie  nerveuse,  Vol.  1,  p 400,  Paris  1909. 
