50 
CHAPTER III. 
INTERNAL STRUCTURE. DIGESTIVE ORGANS. GUL- 
LET, CROP, STOMACH ADAPTATION OF, TO DIFFER- 
ENT HABITS OF BIRDS. GASTRIC JUICE ITS USE 
AND PROPERTIES. GTZZaRD, ITS GRINDING POWERS. 
RESPIRATION OF BIRDS. 
Having briefly pointed out tbe most prominent 
features of tbe skeleton, as influencing tbe general 
form of birds, we shall now proceed to give a short 
sketch of the structure and uses of some of the 
internal parts, commencing with those for the sup- 
ply and consumption of food. The following figure 
may assist our explanation. 
