ANATOMY OF THE WOODPECKER. 



pecker (Gednus viridis), and a reference to the explanation of the lettering on it will give a general 

 idea of the whole. 



The tip of the tongue (t) is a slender, flattened, horny point, bearing on its sides and tipper surface 

 a number of very delicate bristles, or prickles, directed backwards, an arrangement eminently useful 

 to the bird for enabling it to extract its insect food from the recesses to which its beak, by reason of 

 its size and hardness, could not readily, nor with sufficient quickness, gain access. This tip is further 

 rendered a more efficient instrument for this purpose by its being constantly moistened by a very viscid 

 saliva secreted by two particularly large salivary glands (Figs. 2, 3, and 4, s.g.) ; and it was long ago 

 remarked by Sir Charles Bell, in his essay on "The Hand" (Bridgewater Treatise, 1837), that the same 

 muscles that effected the protrusion of the tongue exerted a simultaneous pressure upon these glands, 

 so that the first result of the muscular contraction is to lubricate the tongue, while the rest of its force 

 is spent in shooting it out with marvellous rapidity. 



Behind this barbed and horny tip, the tongue is a slender worm-like body, 

 of which the core is the anterior prolongation of the hyoid bone. The fore-part of 

 this core, more like a bristle than a bone, is known to anatomists as the " glosso- 

 hyal," and it is immediately succeeded posteriorly by the "cerato-hyal."* 

 Behind this is the "basi-hyal" (Fig. 1, b.h.}, the last bone to enter into the 

 formation of the tongue proper. From this basi-hyal springs the pair of bones 

 the " thyro-hyals" which attain the remarkable degree of development for 

 which the birds now under consideration are distinguished. From each side 

 of the hinder portion, then, of this basi-hyal bone diverge these important 

 "thyro-hyals" (Fig. 1, c.br., e.br.). They, in the Woodpeckers 

 (compare Fig. 3, thJi.), extend outwards and backwards to pass 

 one on each side of the neck until they curl upwards and for- 

 wards, converging to meet one another on the upper part of 

 the back of the head ; thence they run along together, ploughing 

 themselves a furrow in the skull-top till they reach almost to the 

 right nostril. Each of these curved and highly elastic bones 

 is surrounded by a delicate sheath, whose inner surface is kept 

 constantly moist and lubricated by its own secretion ; and this 

 sheath is attached to the bone of the skull at its junction with 

 the \ipper mandible, as is shown in the accompanying woodcut Fig. 4. DISSECTION OF 

 (Fig. 3, i). 



Enclosed in the sheath here spoken of, and along the con- 

 cavity of each bone, is a muscle which has a fixed attachment to (After 



HEAD OF GREEN 

 WOODPECKER VIEWED 

 FKOM BELOW. 



3. TJPPER 



the crura of the lower mandible on each side (Fig. 4, e.m., e.m.}. 10 Lower Mandibieim Base 



/ of Tongue; (tk.li.,th. h. >Thyro- 

 The contraction of this mnsr-lp shoots flip tonmift out, in t.wo hyals; (s.g., s.g.} Salivary 



VIEW OF SKULL , . 



OF GREEN woo- 1 "6 contraction ot this muscle shoots the tongue out m two 



PECKER. 



Glands; (m, m) Muscles of 



(After 

 Maogiuivray., 



g !^ gTracheat 



different ways. In. the Green Woodpecker the extremities of 



,1 ,1 i -i ! , ., , trusorMuscles.wliich thrust 



the thyro-hyal bones are themselves attached to the mandible, out the Tongue; (r.m.) Re- 



" ' tractor Muscles of Tongue 



while the curvature of the bones makes a loop that hangs 

 low clown on each side of the neck (see Fig. 2, th.h.). As the 

 muscle is shortened this loop is raised up, and the free tip of the 



tongue is consequently projected ; and since the muscle is on the inner, or concave, side of the curve, 

 a very small shortening on its part makes a great addition to the apparent length of the tongue. Sir 

 Charles Bell elucidates this action by comparing the great effect on the curve of a fishing-rod's 

 flexible top that a small tightening of the line has. But while this is the case in many species, 

 there are others in which the sheath alone is attached to the bones of the forehead, and the bones 

 themselves slide along inside together with the contracting fibres of the muscle, thus producing 

 the same result as was obtained in the other case by the loops hanging low down in the 

 neck. 



Compare Fig. 1, ch. ; this bone usually exists in a paired condition, but in Woodpeckers and some other birds it 

 appears single by the confluence of its members In many birds the "basi-hyal" is succeeded by the "uro-hyal" (Fig. 1, 

 l>. lr.), a bone altogether absent whenever the tongue is capable of extraordinary protrusion. 



