The  kinds  of  disease  to  which  the  spinal  cord  is  liable  are  not  specifically
numerous,  but  those  which  are  common  present  several  varieties.  The  pro-
cesses are  congestion  and  anaemia,  hemorrhage,  inflammation,  degeneration
and  growths.  Hemorrhage  and  growths  are,  on  the  whole,  rare.  Con-
gestion and  anaemia  play  an  uncertain  part  in  the  production  of  symptoms ;
their  influence  has  been  certainly  overrated  by  some  writers,  and  perhaps
under-estimated  by  others.  The  most  frequent  lesions  are  inflammation  and
degeneration.  These  two  processes,  distinct  in  their  typical  forms,  blend  in
their  intermediate  varieties.  Inflammation  varies  much  in  character  and
course.  Its  effects  are,  in  some  cases,  produced  with  great  rapidity,  in
other  cases  with  extreme  slowness.  It  probably  commences  in  most
instances  outside  the  nerve  elements,  which  are  secondarily  involved.  Per-
haps some  acute  processes  in  the  nerve  elements  themselves  are  most  accu-
rately regarded  as  a  parenchymatous  inflammation.  Degeneration  consists
of  two  processes,  a  wasting  of  the  nerve  structures,  cells  and  fibres,  and  an
overgrowth  of  the  connective-tissue  elements.  The  latter  leads  to  the  con-
dition termed  sclerosis.  The  name  has  been  given  to  it,  probably,  because
the  process  is  one  that,  in  other  organs,  increases  their  consistence.  In  the
cord  it  has  not  often  this  effect.  The  newly-formed  connective  tissue  is
rarely  of  greater  firmness,  and  is  often  less  firm,  than  the  nerve  elements  it


168  SPINAL    CORD.
