^  The  term  Sarcoma  has  recently  been  revived  by  Tirchow,  and  other  pathologists
in  Germany,  and  employed  to  designate  a  group  of  tumours,  '  the  tissues  forming
which  belong  to  the  series  of  connective  substances,  but  which  are  distinguished  from
the  tumours  formed  of  the  connective  tissues  by  the  preponderating  development  of
the  ceE-elements.'  The  tissae  of  granulations  formed  during  the  inflammatory  irritation
of  the  connective  tissue  is  regarded  as  the  normal  prototype  of  those  tumours.
The  following  varieties  of  sarcoma  have  been  described : —

u.  Tumours  with  spindle-shaped  cells,  the  fibro-plastic  cells  of  Lebert  (Spindel-
zellen-sarcoma.  Recurrent  fibroid  tumours,  Fibro-plastic  tumours).
b.  Tumours  with  colossal,  many-nucleated,  or  myeloid  cells  (Riesen-zellen-sarcoma,
Myeloid  tumours).
t.  Tumours  with  small  round  cells  like  the  lymph  or  white  blood-corpuscles,  or
pus,  or  granulation-cells  (Rund-zellen-sarcoma,  Granulations-  sarcoma,  Glio-  or  Lympho-
sarcoma).
d.  Tumours  with  stellate  cells,  and  a  gelatinous,  shiny,  intercellular  substance,  not
unlike  the  material  found  in  a  myxoma  (Myxo-sarcoma).
0.  Tumours  with  round  or  variously-shaped  cells,  most  of  which  are  of  large  size,
and  are  usually  imbedded  in  a  fibrous  matrix.  In  structure  no  well-defined  character
distinguishes  these  tumours  from  Carcinoma.
/.  Tumours  in  which  the  cells  contain  a  considerable  proportion  of  pigment,  which
is  most  frequently  found  in  the  cells  described  in  the  last  group,  in  the  tumours  with
round  and  with  fusiform  cells  (Pigment-sarcoma,  Melanoma).
In  all  these  forms  an  intercellular  substance  occurs,  which  may  be  either  homo-
geneous or  fibrous,  or  which  may  present  a  delicate,  net-like  or  trabecular  structure,
such  as  is  found  in  a  lymphatic  gland.
But  the  tumours  classed  under  the  name  of  sarcoma  vary  also  greatly  in  their
general  characters,  and  in  the  localities  in  which  they  grow  :  pendulous  growths  from


542  MYELOID  TUMOUBS.
