PHAGOCYTIC  FUNCTION  OF  VARIOUS  TYPES  OF  CELLS     59

Both  types,  however,  are  capable  of  taking  up  foreign  cells  when
these  are  introduced  from  without,  although  it  lies  in  the  nature  of
their  differing  mobility  (the  granular  leukocytes  being  essentially
mobile  and  the  macrophages  sessile)  that  the  former  play  a  more
important  role  in  the  actual  conflict  between  the  invading  cells  and
the  defensive  forces  of  the  host.  That  the  polynuclear  neutrophilic
leukocytes  more  especially  will  take  up  bacteria  and  protozoa1  has
been  known  for  many  years,  and  has  been  demonstrated  not  only
in  vitro,  but  manifestly  occurs  also  in  the  living  body,  as  is  sug-
gested by  the  findings  in  gonorrheal  pus,  in  the  cerebrospinal
exudate  of  epidemic  cerebrospinal  meningitis,  in  the  peritoneal  fluid
of  general  peritonitis,  etc.,  where  many  of  the  offending  organisms
may  be  found  enclosed  in  leukocytes.
The  enormous  extent  to  which  phagocytosis  of  bacteria  may  go
is  well  illustrated  by  the  following  example  which  came  under  my
observation  a  few  years  ago.  In  a  patient  who  was  dying  from
epidemic  cerebrospinal  meningitis  we  could  demonstrate  the  presence
of  meningococci  directly  in  the  stained  preparation  and  calculated
their  actual  number  to  be  7,380,000  per  cubic  centimeter.  The  vast
majority  of  these  were  enclosed  in  polynuclear  neutrophiles  and  in
large  mononuclear  cells  which  I  was  inclined  to  view  as  endothelial  cells.
