﻿50 ON THE CLASSIFICATION OF BIRDS. 



should be the chief instrument of procuring food ; it is 

 therefore large and fleshy. But in birds which gulp 

 their food the instant it is captured, the tongue apparently 

 is of no sort of use ; it is therefore reduced to a mere 

 rudiment : such is the case with the swallows and night- 

 jars. There must be something very analogous to the 

 same mode of feeding in the genus Casmorhynchus ; for 

 on dissecting more than one specimen of C. nudicollis, we 

 found the tongue fully as small, and the mouth as wide, 

 as in the ordinary Caprimulgidce. The food of the duck 

 is discriminated solely by the tongue, while that of the 

 swallow is selected by the eye ; and hence this remarkable 

 difference in their respective tongues. Hitherto we have 

 noticed those forms only in which the length of this 

 member is regulated by that of the bill; but there is 

 another structure which is not uncommon, and by which 

 the bird is able to protrude it to twice its usual length; 

 hence such tongues are called extensible : of these there 

 are two distinct modifications, — one possessed by the 

 woodpeckers, the other by the honeysuckers. On opening 

 the bill of a woodpecker, immediately after it is killed, 

 the tongue seems to be of the ordinary length, rather 

 short, and shaped vey much like the heads of those 

 spears used by the Carters of Southern Africa, and called 

 assagais, being pointed at the end, with numerous little 

 barbs on the sides : this, however, is only the head or 

 point of the tongue ; draw it out of the mouth, and a 

 person unacquainted with its formation would fancy he 

 had got hold of a very long earth-worm, which the bird 

 had incautiously devoured, and which had stuck in its 

 throat. This description, unscientific though it be, will give 

 the reader a much better idea of the tongue of the wood- 

 pecker, than the most elaborate anatomical character we 

 could draw up. A tongue so formed, in allusion to the ap- 

 pearance it assumes, is called vermiform : the point re- 

 poses, in the ordinary manner, between the mandibles of 

 the bill; the rest is concealed, and from being elastic is 

 capable of being thrown out, at the pleasure of the bird, 

 to four or five times the length of the bill itself. This 



