As  in  other  classes  of  animals,  the  whole  alimentary  canal
of  birds  varies  much  in  its  length  and  capacity,  and  in  the
form  and  development  of  its  cavities,  according  to  the  nature
of  the  food,  being  long  and  capacious,  with  large  glandular
organs  and  muscular  parietes,  in  the  various  phytophagous
tribes,  and  with  the  reverse  of  these  characters  in  those  which
feed  more  exclusively  on  animal  food.  The  long,  wide,  mus-
cular oesophagus,  with  a  smooth  mucous  coat,  and  thin  epi-
dermic lining,  passes  down  behind  and  a  little  to  the  right
side  of  the  trachea,  as  seen  in  the  annexed  figure  of  the  vis-
cera of  the  gallus  domesticus,  (Fig.  128.  a,}  and  about  the
middle  of  its  course,  a  little  above  the  two  anchylosed  clavi-
cles, it  presents,  in  gallinaceous,  raptorial,  and  many  other  birds,
an  enlargement,  an  ingluvies  or  crop,  (128.  b.)  varying  in  form
and  structure  according  to  the  difference  of  the  food,  and


ORGANS    OF    DIGESTION.
provided  with  numerous  glandular  follicles  situate  between  the
mucous  and  the  muscular  coats.  Continuing  downwards  behind
and  a  little  to  the  right  of  the  trachea,  and  behind  the  heart,
(128.m,)  and  great  branches  of  the  aorta,  the  oesophagus  passes
forwards  below  the  inferior  larynx,  between  the  two  lobes  of
the  lungs,  (128.  n.  n})  and  to  the  left  side,  to  dilate  into  a


second  gastric  cavity,  the  glandular  stomach,  proventriculus,
infundibulum,  or  ventriculus  succenturiatus,  (128.  c,)  which  is
highly  vascular  and  provided  with  more  numerous  and  larger
follicles  than  open  into  the  crop.  Beneath  the  vertical  in-
fundibulum is  the  powerful  muscular  gizzard,  (128.  d.)  dis-
posed transversely  from  left  to  right,  like  the  ordinary^sto-
mach  of  most  vertebrata,  covered  with  the  lobes  of  the  liver,


400  ORGANS    OF    DIGESTION.
