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TEXT-BOOK OF ZOOLOGY 



(d) The strong bones of the skull afford a firm support to the chisel-like 

 action of the beak, and are capable of withstanding powerful shocks. 



5. The insects are pulled out of their crevices and galleries by means 

 of the peculiarly-constructed lingual apparatus. The tongue itself (Z.) is 

 small, horny, and provided with a few sharp barbs on each side at its 

 tip. Posteriorly it is united with a rod-shaped bone, the hyoid. The 

 latter lies within a muscular sheath (Z.Sch.), which when at rest is 

 contracted in vermiform fashion, and at its posterior end is connected 

 with two other bones, the hyoid cornua (Zh). These are very flexible, 

 and extend from behind forwards over the occiput to the base of the 

 beak, sliding freely in a muscular sheath, which is attached at the point 

 of union of the rami of the mandible (Vm.). By the contraction of this 

 muscle (shown in the form of folds below Zh II.) the horns are drawn 



HEAD AND NECK OF SPOTTED WOODPECKER, WITH SKIN 



REMOVED. 



Tongue retracted ; II., tongue protruded (somewhat shortened) ; 

 N., nostril; HI., horny bar on upper bill; 0., opening of 

 ear-passage ; L., trachea ; Sp., oesophagus. The dotted lines 

 indicate the position of the hyoid cornua below the salivary 

 gland (D) when the tongue is protruded. The other letters 

 are explained in the text. 



down towards the nape of the neck (their ends coming to lie at Zh II.), 

 and push the hyoid bone forwards. This has the effect of extending the 

 vermiform sheath of the hyoid into a smooth cylinder (like an earth-worm 

 when extended), and the tongue is consequently protruded far forwards 

 from the beak. (Compare with the tongue of humming-birds, chameleon, 

 and snakes.) On account of its extraordinary length, thinness, and eel- 

 like flexibility, the organ penetrates with ease into the borings of grubs 

 and can even follow their windings. The larger insects are pierced by 

 the horny tip of the tongue (really forming a barbed arrow-head) ; the 

 smaller are, as it were, glued on to the tongue by a very viscid saliva, 

 which is abundantly secreted by large salivary glands (D). The tongue 

 is always completely smeared over with this fluid, so that insects stick to 

 it like " flies to a limestick." The tongue is retracted by the muscles of 

 the sheath (Z.Sch.) and several other muscles, some of which (Bm.) are 

 indicated in the illustration. 



