In  the  nerves,  morbid  changes  are  constantly  found.  They  are  always
intense  in  the  intramuscular  twigs,  and  in  the  branches  from  which  these
twigs  proceed.  They  are  usually  considerable  in  the  larger  trunks,  but
commonly  become  slighter  the  further  from  the  periphery  the  nerve  is
examined.  Sometimes  a  few  degenerated  fibres  can  be  traced  throughout
the  nerves.  The  affection  of  the  nerve  seems  to  begin  by  a  change  in  the
medullary  sheath,  which  becomes  narrower,  cloudy  and  granular,  the  axis
cylinder  being  intact  and  the  outer  sheath  and  nuclei  presenting  little  altera-
tion. With  this,  however,  is  combined  a  more  considerable  change  resem-
bling the  "  Wallerian"  degeneration  that  is  secondary  to  a  lesion  of  a  nerve
(see  p.  60).  The  myelin  undergoes  segmentation,  the  axis  cylinder  also
breaks  up,  the  nuclei  and  protoplasm  of  the  sheath  become  increased,  and
the  products  of  this  degeneration  accumulate  in  masses  of  myelin  and
granule  corpuscles.  The  slighter  change  (which  Gombault,*  who  first
described  it,  termed  "  peri-axial  neuritis  ")  is  sometimes  segmental,  affecting
short  tracts  of  the  nerve,  that  are  separated  by  normal  portions,  or  the  upper

*  Arch,  de  Phys.,  vol.  v,  p.  592.
PATHOLOGY.  1267

part  of  the  degenerated  region  may  present  only  the  change  in  the  medullary
sheath,  while  in  the  lower  part  there  are  the  more  extensive  alterations.
