124 THE GREEN WOODPECKER. 



It is to this bone that the muscles which protrude and 

 retract the tongue are attached. 



The cornua are more elongated in birds than in mammals, 

 and they project towards the back of the neck, being quite 

 distinct from the skull in most cases. 



In the woodpecker, however, these horns, after passing 

 backwards on each side of the neck, curl first upwards 

 and then forwards, and converge to meet each other at the 

 vertex of the head. They now run in a special furrow in 

 the bone, on the top of the skull, curl round the right orbit, 

 and are finally attached to its inner margin. These curved 

 bones are highly elastic, and are contained within a sheath, 

 together with a muscle which lies on and is attached to 

 their concave side. This muscle has also a fixed attach- 

 ment to the lower mandible. Hence, when it contracts, the 

 loop, which the hyoid bone forms in the neck, is first raised, 

 and then carried forwards, with the result that the free tip 

 of the tongue is widely protruded. 



Sir Charles Bell states that the same muscle which causes 

 the protrusion of the tongue, also exerts pressure on a large 

 salivary gland, by which means a drop of highly viscid 

 secretion is poured out on the barbed extremity of the 

 tongue, thus enabling the bird with great ease and rapidity 

 to convey to its mouth small insects, such as ants, which 

 when touched by the tongue instantl}'- adhere to it. By the 

 simple contrivance of the muscle being placed on the inner 

 or concave side of the loop previously spoken of, a very 

 slight shortening of the muscle causes remarkable increase 

 in the length of the tongue. The organ is withdrawn into 

 the mouth again by muscular power, which action is 

 greatly assisted by the elasticity and springing back of 

 the prolongations of the hyoid bone. The woodpecker de- 

 pends to a very large extent on its tongue for procuring 



