84 COMPARATIVE ZOOLOGY. 
In Birds, the length of the alimentary canal varies with 
their diet, being greatest in those living on grain and fruit. 
The gullet corresponds in length with the neck,, which is 
longest in the long-legged tribes, and in width with the 
food. In those that swallow large fish entire, the gullet 
is dilatable, as in Snakes. In nearly all Birds, the food is 
delayed in some cavity before digestion : thus, the Pelican 
has a bag under the lower jaw, and the Cormorant lias a 
capacious gullet, 
where they store 
up fishes; while 
those that gorge 
themselves at in¬ 
tervals, as the 
Vulture, or feed 
on seeds and 
grai ns,as the Tur¬ 
key,have a pouch, 
called the crop, 
developed near 
the lower end of 
the gullet. 45 The 
Ostrich, Goose, 
Swan, most of 
the Waders, and 
Fig. 49 .—Stomach of the Crocodile: a r mwscnlar fibres ra- • 
diating from a central tendon, b; d, commencement of tlie trUlt 01 m- 
duodenom; c r oesophagus; /,intestine. Sect eating Birds, 
which find their food in tolerable abundance, and take it 
in small quantities, have no such reservoir. Pigeons have 
a double crop. 
In all Birds, the food passes from the gullet into the 
proventriculus , or stomach proper, where it is mixed with 
a “gastric juice” secreted from glands on the surface. 
Thence it goes into the gizzard, an oval sac of highly 
muscular texture, and lined with a tough, horny skin. 48 
