The  peculiarity  of  Pertussis,  or  Hooping-cough,  lies  in  the  ner-
vous, or  rather  the  muscular,  relations  of  respiration.  The  affection
is  at  first  distinctly  inflammatory,  and  the  cough  is  not  unlike  that  of
common  bronchitis  ;  but  it  soon  assumes  a  convulsive  character,  the
fits  of  coughing  being  very  violent,  uncontrollable,  shaking  the  whole
frame,  and  often  ending  with  retching.  There  may  be  a  whooping
sound  in  the  inspiration  during  the  cough,  but  not  necessarily  ;  and
this,  as  we  have  before  noticed,  depends  on  an  undue  irritability  of
the  bronchial  and  contractile  laryngeal  muscles,  so  that  they  do  not
relax  as  usual  during  the  act  of  taking  breath.  During  this  whoop,
or  sonorous  back  draught,  the  ear  applied  to  the  chest  hears  little  or
no  natural  respiratory  murmur  ;  but,  during  the  intervals  of  the
cough,  this  murmur  may  be  as  distinct  as  usual.  This  does  not
necessarily  imply,  however,  as  Laennec  supposed,  that  there  is  a
spasm  in  the  bronchi  ;  the  upper  part  of  the  tube  being  narrowed,  is
sufficient  to  weaken  much  the  sound  of  vesicular  respiration,  as  it  is
observed  in  oedema  or  spasm  of  the  glottis,  and  where  aneurisms  or
other  tumors  press  on  the  windpipe.
