Structure. — These  cells  are  about  the  hardest  of  all  to  study,  being  so  sensi-
tive. Various  methods  have  been  applied  to  demonstrate  their  structure,  and  each
has  shown  a  different  one.  Foa's  description,  a  peripheral  structureless  haemo-
globin-containing layer,  a  middle  with  a  net-work  of  fibres  enclosing  granules,  and
a  centre  of  homogeneous  protoplasm,  is  one  of  the  most  elaborate  and  often
quoted.  The  consensus  of  opinion  now  is  that  all  of  the  fibres,  layers,  etc.,  are
artefacts;  that  the  various  granular-like  bodies  seen  in  the  fresh  cells  are  not  an
essential  part  of  the  cell ;  that  those  in  the  stained  are,  some  at  least,  precipi-
tates of  the  fixing  agent,  or  of  the  stain;  and  that  structure,  although  it  cer-
tainly exists,  is  yet  to  be  demonstrated.  Ehrlich  considers  that  heat  is  the  best
fixative,  because  it  gives  a  homogeneous  cell  without  structure.  This  argument
seems  weak,  for  heat  renders  difficult  of  observation  the  structure  of  many  other
cells  of  similar  nature,  including  the  protoplasm,  but  not  the  granules,  of  leuco-
cytes, and  hence  may  be  the  very  worst  method  for  the  study  of  red  cells.
