Hiccough  is  occasionally  observed  after  excessive  or  injudicious  eating  or
drinking,  in  gastric  disorders,  peritonitis,  the  so-called  typhoid  state,  and
ursemia.  It  occurs  also  in  hysteria  and  may  constitute  a  pure  neurosis.
The  hiccough  of  cerebral  disease,  as  hydrocephalus  or  meningitis,  is  doubt-
less the  result  of  irritation  of  the  central  origin  of  the  phrenic  nerve.  The
writer  knows  a  gentleman  in  whom  certain  kinds  of  tobacco  invariably
produce  distressing  hiccough,  while  others  can  be  smoked  with  impunity.
446  MEDICAL  DIAGNOSIS.
Persistent  and  intractable  hiccough  occasionally  attends  the  cIosiDg  dajrs  of
fatal  illness  and  in  rare  instances,  occurring  as  a  neurosis,  has  caused  death
by  exhaustion.
Of  all  the  special  or  modified  respiratory  movements  cough  has  the
most  important  bearing  upon  diagnosis  and  therefore  requires  more  ex-
tended consideration.
SIGNIFICANCE  OF  COUGH  IN  DIAGNOSIS.
Etiolos^fcal  Considerations. — Reflex  Cough. — Cough  in  the  vast  ma-
jority of  instances  is  the  result  of  reflex  irritation  of  the  terminal  nerve  fila-
ments of  the  vagus  distributed  to  the  respiratory  tract.  Irritation  of  the
mucous  membrane  of  the  larynx  above  the  vocal  cords  does  not  produce
cough  but  causes  gagging,  while  irritation  below  the  cords  gives  rise  to
cough.  Especially  sensitive  areas  are  the  interarytenoid  space  and  the
region  of  the  bifurcation,  while  the  general  mucous  membrane  of  the
trachea  and  bronchi  shows  a  scarcely  inferior  irritability.  Lesions  of  the
lung  parenchyma  probably  do  not  cause  cough,  though  they  are  usually
connected  with  pathological  conditions  of  the  bronchi.  Pleural  irritation
is  commonly  attended  by  this  symptom.  The  aspiration  of  a  pleural
exudate  is  frequently  followed  by  prolonged  and  violent  cough.
