Then  in  the  production  of  these  dilata-

JWi/lHi  ^\  ^ }  ^\      tions  we  are  not  to  forset  the  influence
.../'Si)  >Sn)  ^i  /  *\        of  violence  in  the  acts  of  respiration.
They  have  been  observed  especially
to  succeed  to  hooping-cough  and  other
bronchial  affections  in  which  the  cough
is  particularly  violentand  long-continu-
ed. The  effects  of  these  violent  acts  of  breathing  may  be  twofold  ;
they  may  cause  the  dilatations  by  the  prolonged  and  forcible  inspira-
tion in  the  manner  already  described  ;  and  they  may  increase  them
irregularly  when  so  distended,  by  the  sudden  pressure  of  the  expi-
ratory forces  upon  them.  But  I  have  met  with  cases  of  dilated
bronchi  in  which  there  had  been  very  little  cough,  and  none  of  any
violence  ;  and  here  we  must  suppose  that  the  other  conditions,  the
irregular  introduction  of  air  and  the  yielding  of  the  membranes,
were  more  exclusively  concerned  in  the  production  of  the  lesion.
