Ehrlich  believed  the  true  lymphocyte  came  from  the  lymph-glands;  others  say
from  the  bone-marrow.  Some  have  tried  to  distinguish  morphologically  those  from
the  marrow  from  those  from  glands  (Rubenstein).  The  question  now  is,  "Do
any  come  from  lymph-glands  ?"  thus  admitting  that  typical  "  lymphocytes"  are  an
important  constituent  cell  of  the  marrow.  Michaelis  and  Wolff  tried  to  differen-
tiate these  cells  on  the  basis  of  their  future  history,  the  lymphocytes  from  lymph
glands  remaining  such,  the  "  lymphoid"  cells  of  the  marrow  being  capable  of  further
development  to  a  granular  cell.  But  this  capability  does  not  aid  us  much  in  saying
which  the  individual  cell  now  before  us  is,  although  these  writers  did  describe
slight  differences  in  their  staining  reactions.  And  yet  this  distinction  between
lymphocytes  and  lymphoid  cells  is  probably  just.  Many  workers  fall  back  upon
such  indifferent  lymphoid  cells  as  young  forms,  naming  them  "  protoleucocytes*'
(Osier),  etc.,  and  consider  that  from  them  develop  colorless  cells  which  cor-
respond to  the  leucoblast  and  erythroblast  of  Lowit  and  Howell,  and  from  these
the  whole  series  of  reds  and  whites.  The  lymphocyte  with  diffusely  staining  notched
nucleus  (Rieder's  cell)  is  probably  an  old  form  of  lymphocyte.  The  small
mononuclears  with  round  vesicular  nucleus,  delicate  chromatin  net-work,  and  rather
broad  band  of  basophilic  protoplasm  with  smooth  margin,  are  young  cells  which
resemble  only  in  appearance  those  of  the  normal  blood,  and  themselves  do  not
belong  there.  The  lymphocytosis  of  young  babies  is  unquestioned,  and  yet  the  most
rational  explanation  for  this  is  that  there  is  an  overproduction  of  leucocytes  which
did  not  exist  at  birth,  since  then  there  was  no  function  for  the  cell.  Yet  this  would
mean  that  young  leucocytes  are  lymphoid  cells.  The  same  might  be  said  for  the
lymphocytes  of  the  digestive  leucocytosis.
