AVES. 



259 



surrounded by a circle of naked skin, constituting what is 

 called the " cere," and this, too, serves as an organ of touch. 

 The tongue of birds can rarely be looked upon as an organ of 

 taste, since it is generally cased in horn, like the mandibles. 

 It is principally employed as an organ of prehension, but it is 

 soft and fleshy in the Parrots, and in them, doubtless, acts as 

 an organ of taste. Salivary glands are always present, but 

 they are rarely of large size, and are often of extremely simple 

 structure. In accordance with the length of the neck, the 

 gullet is usually very long in birds, and is generally very di- 

 latable. In the ilesh-eating and grain-eating birds the gullet 

 is dilated (Fig. 130, c) into a pouch which is called the 



cl 



Fia. IBO.— DigestiTO System of the common Fowl (after Owen), o Gnllet ; c Crop • « Pro- 

 vontriculus; g Gizzard; «m Small intestine; * Intestinal caeca; I Large intestine: 

 o2 Cloaca. ' " ' 



" crop," and is situated in the lower part of the neck, just in 

 front of the merry-thought. This may be simply a dilatation 

 of the tube of the gullet, or it may be a single or double 

 pouch. The function of the crop is to detain the food, for a 

 longer or shorter period, according to its nature, before it is 

 submitted to the action of the proper digestive organs. In the 

 Pigeons, the food which has been previously softened in the 



