THE EDINBURGH 



JOURNAL OF NATURAL HISTORY, 



AND OF 



THE PHYSICAL SCIENCES. 



AUGUST, 1839. 



DESCRIPTION OF THE APPARATUS BY WHICH THE TONGUE IS EXTENDED IN 

 THE FAMILY OF WOODPECKERS. 



The singular apparatus by means of which the Woodpeckers are enabled 

 to secure their prey has often been described, but generally in an imper- 

 fect, and often, in some respects, in an erroneous manner. Having re- 

 cently examined individuals of several species, we are enabled to present 

 a detailed account of the subject. In the first place, let us take the Ivory- 

 billed Woodpecker, Picus principalis, one of the largest species known. 



Fig. 1 represents — The 

 upper and lower mandibles, 

 a b, the tongue, c d, the ter- 

 minal barbed portion, c, the 

 fleshy part, d, the oibit and 

 eye, e, the salivary gland of 

 the right side, /, the hyoid 

 bones, gg, the neck, hh, the 

 furcula, 2 i, the oesophagus, 

 jj, the trachea, k, its lateral 

 muscles, 1 I, the cleido-tra- 

 cheal muscles, m m. In fig. 

 2 are seen — The lower 

 mandible, b, the salivary 

 glands, ff, the hyoid bones, 

 gg, the oesophagus, j j j, 

 the trachea, k, the lateral 

 muscles, / I, the cleido-tra- 

 cheal, m in, the glosso-laryn- 

 geal, n n, the muscles by 

 which the tongue is exserted, 

 o o. 



The bill of this species, 

 Fig. 1, a b, measures three 

 inches and two-twelfths from 

 the angle of the mouth ; and 

 the tongue, c d, which lies 

 in the broad groove of the 

 lower mandible, reaches to 

 two-twelfths of the extremity, 

 but at the will of the bird may be exserted so as to extend 3J- inches 

 beyond the point of the bill. The tongue itself presents the appearance 

 of a slender worm-like body, having a middle longitudinal groove on its 

 tipper surface, which is transversely wrinkled, and terminated by a slender 

 tapering bony point, of which the margins and part of the upper surface 

 are covered with acicular prickles, which are in some degree moveable 

 and directed backwards, but not capable of being bent outwards, much 

 less in the direction of the tip of the tongue. The length of this organ is 

 apparently two inches eight-twelfths ; but if measured from the base of the 

 basi-hyal bone, only one inch eleven-twelfths ; its breadth at the base two 

 and one-half-twelfths, slightly tapering to the end of its fleshy part, where 

 it somewhat suddenly contracts, so as to have a breadth of little more 

 than one-twelfth. The length of the horny tip is nine-twelfths. The 

 tongue at the base is entirely destitute of the lobes and papillae which in 

 other birds give it a sagittate appearance ; and there is no uro-hyal bone, 

 which in them slips into a groove along the front of the thyroid bone of 

 the larynx. The mouth is of moderate width, its breadth being, as al- 

 ready mentioned, eleven-twelfths, it being in this respect very[ different 

 7 



A 



from that of Flycatchers, Goatsuckers, Swallows, and such birds as 

 seize on living insects while on wing. The lower mandible is deeply con- 

 cave within, wider than the tongue, and covered with mucous membrane 

 until one inch five-twelfths from the point, beyond which it is horny, with 

 a median groove, near the commencement of which is a small aperture 

 for the ducts of the salivary glands. The tongue is capable of bein" re- 

 tracted ten-twelfths of an inch from the tips of the mandibles, and is then 

 seen to slide into a sheath, formed by an induplieation or intussusception 

 of the membrane covering it, and having two franula of elastic tissue in- 

 serted into the angle of the jaw. Here it may be proper to state, that in 

 birds generally the bony elements of the tongue are seven, as may be re- 

 presented by the accompanying diagram, in which the 

 first or upper piece is named the glosso-hyal, the next 

 the basi-hyal, the third, in the same line, the uro-hyal ; 

 the two coming off from the base of the second piece or 

 basi-hyal, are the apo-hyal, to each of which is appended 

 another, the cerato-hyal. The tongue itself is in no de- 

 gree extensile or contractile, but has for its solid basis a 

 very slender basi-hyal bone, one inch two and one-half- 

 twelfths in length, terminated by a glosso-hyal bone half 

 an inch in length, but, as already said, has no basal or 

 uro-hyal bone, which, on account of the unusual extent of its motion, 

 would form an impediment. 



From the base of this basi-hyal bone there proceed, backwards and 

 slightly diverging, two slender apo-hyal bones one inch one-twelfth in 

 length, each of which is continuous, with an extremely elongated cerato- 

 hyal bone, four inches and one-twelfth in length, three-fourths of one- 

 twelfth in breadth at the commencement, gradually tapering to a 

 blunt point, convex on its lower surface, concave or channelled on the 

 upper, passing under and internally of the articulation of the jaw, and 

 curving upw-rrds along the occiput, until the two meet on the top of the 

 head, at the level of the posterior margin of the orbit, in the median line 

 of the cranium, which is much depressed, whence they proceed in mutual 

 contact, inclining slightly to the right side, and terminate a little before 

 the anterior margin of the orbit, half an inch behind the right nostril, and 

 a quarter of an inch from the base of the bill. These prolongations of 

 the os hyoides, being of an osseo-cartilaginous nature, are possessed of 

 much elasticity, so as in some measure to resemble a curved spring. 



From near the angle or point of union of the two crura of the lower 

 mandible internally, there proceeds on each side a slender muscle, oo, 

 which, running backwards, comes in contact with the prolongation of the 

 hyoid bone, at the joint between the apo-hyal and cerato-hyal portions, 

 and is thence continued along the whole extent of the latter, og, eg, run- 

 ning chiefly along its upper side, but partially inclosing it, and bound to 

 it by a sheath of cellular tissue, which allows it considerable motion. 

 The bone and muscle together are inclosed in an extremely delicate, trans- 

 parent, tenacious sheath, moistened internally with a serous fluid, and 

 terminating at the end of the bone, where it is attached by elastic tissue 

 to the cellular substance and periosteum near the base of the bill. This 

 delicate sheath, perfectly smooth and lubricated on its inner surface, is on 

 the outer attached by delicate filaments to the dense cellular tissue which 

 forms a kind of external sheath. It is fixed in its place, and the hyoid 

 bone, with its muscle, gg, slides backwards and forwards in it. 



The entire length from the tip of the tongue, c, to the tip of each pro- 

 longation of the hyoid bone at e, is seven inches two-twelfths. The pro- 

 trusion of the tongue is effected by the contraction of the slender muscle 

 above described, o, which having a fixed basis in the lower jaw near its 



