In the preceding examples the length of the tongue never exceeds that of the bill; but in the case of the woodpeckers it is protrusible to a wonderful extent. On opening the bill of a woodpecker immediately after it has been killed, the tongue seems of ordinary length, or indeed rather short, and shaped somewhat like the spears used by the Caffres in South Africa, called _assagais_, pointed at the end and furnished with numerous barbs. (See Fig. 10.) This, however, is only the tip of a very remarkable instrument. If the barbed portion be drawn out of the mouth, a person unacquainted with its nature would think that he had got hold of a very long earthworm that the bird had incautiously tried to swallow, but which had stuck in its throat; hence a tongue of this description is called _vermiform_. The point in its usual position reposes in the ordinary manner between the mandibles; the rest is concealed, but is susceptible of extension, at the pleasure of the bird, to four or five times the length of the bill. The act of protrusion is effected by the remarkable structure of the root of the tongue, or more properly of the _os hyoides_, or bony apparatus whereby it is attached. The posterior prolongations derived from the _os hyoides_ are compactly curved around the back of the skull; and occasionally they are prolonged forwards to such an extent as actually to reach the nostrils. By means of this somewhat complex arrangement the woodpecker, having broken away the bark of a tree by the powerful strokes of its bill, and thus laid open the retreat of the insects beneath, suddenly darts out its tongue, spears its prey, and instantly brings the transfixed insect into its mouth. The SENSE OF TOUCH must be of very limited utility; indeed, there seems to be no part of the body of a bird so constructed as to be capable of tactile impressions. The wings, the representatives of hands and arms, are obviously entirely unfit for the exercise of such a function; neither do the legs and feet seem to be better suited to this purpose. The only organ of touch about which there can be no doubt is the bill, yet even this is generally covered with a hard sheath of horn. Nevertheless, in some races the extremity of the bill is soft and largely supplied with nerves. In snipes and wood-cocks, for example, the sensitive extremity of the beak materially assists in procuring their food.