114 COMPARISONS OF STRUCTURE IN ANIMALS. 



neck extended to the stretch, and buried in the 

 water, the beak being at work in the oozy bed 

 of the river, will feel convinced, on a moment's 

 reflection, of the delicacy of discriminating 

 sensibility which that organ must possess. 

 Anatomy confirms the fact. 



The woodpeckers constitute a group of birds 

 in which the toneue is an essential agent in the 

 acquisition of food. The tongue is long, flex- 

 ible, capable of being protruded to a great 

 distance, covered with viscid saliva, and armed 

 with a horny tip, barbed on each side Avith 

 minute spines directed backward. This instru- 

 ment the woodpecker launches forth with great 

 rapidity, inserting it into chinks and crevices 

 where insects lodge, or into their cells and 

 mazy retreats beneath the mouldering bark of 

 trees, which the bird first lays open by strokes 

 with its powerful beak; it catches them on the 

 barbed and glutinous point, and draws them 

 instantaneously into the mouth. The tongue of 

 the woodpecker is at once a flexible sensitive 

 probe, and an efficient agent in the acquisition 

 of food. The same observation applies to the 

 long worm-like tongue of the wryneck, Avhich 

 is covered with a glutinous secretion, and 

 which the bird inserts into thg crevices of the 



