160 MANDIBLES. 



birds, but their interior is filled with a hard fibrous sub- 

 stance, adding to their general strength and solidity. 

 They are worked by muscles, fitted to enable them to 

 destroy such captives as are infolded in the animal's 

 arms. In the nautilus, the mandibles are blunt, and 

 of a calcareous texture, and are calculated for crushing 

 the shells of mollusks. The mandibles of the cephalo- 

 pods enclose a muscular tongue ; it is invested with a 

 membrane of a delicate structure, but it is armed be- 

 sides with recurved, horny, hook-like papillae, by means 

 of which the morsels of food, cut off from the mass 

 by the mandibles are retained in the mouth, and then 

 by a vermiform or undulatory action of the tongue, 

 forced backwards into the gullet. Salivary glands 

 pour an abundance of saliva into the mouth. The 

 gullet conducts to a large crop, lined with a glandular 

 folded membrane ; and from this crop a short tube 

 leads to a strong muscular gizzard, not unlike, in 

 structure and lining, to that of a common fowl. Here 

 the food is ground to a soft mass. From this giz- 

 zard proceeds the intestinal canal, receiving the bile 

 from a large liver divided into numerous lobules. The 

 intestinal canal is simple, and terminates at the base of 

 the funnel ; into which latter (excepting in the nautilus,) 

 is also poured the inky secretion of a capacious pouch, 



