ease  of  the  posterior  columns  is  great.  Often,  however,  in  old  cases,  there
is  a  slight  general  increase  in  the  connective  tissue  throughout  the  cord.
Sometimes  there  is  distinct  sclerosis  of  other  definite  tracts.  The  ascending
antero-lateral  tract  may  be  degenerated  above  the  lower  dorsal  region,  below
which  it  seems  not  to  exist ;  the  fibres  probably  pass  to  it  from  the  posterior
commissure  in  the  lower  dorsal  region.  An  example  of  this  degeneration  is
shown  in  Fig.  in.  The  direct  cerebellar  tract  is  also  occasionally  diseased,
but  certainly  less  frequently  than  has  been  alleged.  In  rare  cases  there  is  a
distinct  degeneration  of  the  pyramidal  tracts.  The  peripheral  layer  of  the
antero-lateral  column  is  occasionally  the  seat  of  sclerosis,  the  connective
tissue  extending  in  from  the  pia  mater ;  this  is  usually  also  thickened,  appa-
rently from  chronic  inflammation,  which  will  be  again  referred  to.
