During  the  pause  the  pupils  often  contract,  and  the  heart's  action  becomes
less  frequent.  The  period  of  arrest  lasts  from  five  to  forty  seconds,  and  the
duration  of  each  cycle  may  be  from  fifteen  to  seventy-five  seconds,  and  may
vary  from  day  to  day.  The  number  of  respirations  in  each  cycle  never
exceeds  thirty.  This  peculiar  phenomenon  is  met  with  in  other  diseases
besides  those  of  the  brain.  It  occurs  in  heart  disease  (in  connection  with
which  it  was  first  studied),  and  in  uraemia,  and  has  also  been  observed
(chiefly  in  children)  in  rare  cases  of  typhoid  fever,  scarlet  fever,  diphtheria,
influenza,  pneumonia,  whooping  cough  with  inanition,  and  opium  poison-
ing. In  general  maladies  it  is  a  less  grave  sign  than  in  disease  of  the  brain,
and  several  cases  of  recovery  are  on  record.  In  brain  disease  the  patient
is  almost  always  comatose,  but  in  other  cases  consciousness  has  been
retained,  and  the  symptom  has  been  known  to  continue  for  as  long  as  forty
days.*

A  form  of  respiration  which  must  be  distinguished  from  that  just  described
consists  of  periods  of  deep  and  energetic  breathing,  which  begin  suddenly  ;
the  respirations  gradually  lessen  in  depth  until  they  cease,  and  after  a  period
of  stillness  energetically  recommence.  The  sudden  commencement  is  the
distinction  of  this  form.  In  another  variety,  seen  by  Biotf  in  meningitis,
the  periods  of  deep  breathing  not  only  commence  suddenly,  but  end  sud-
denly.
