80 DESCRIPTIONS OF THE GROUPS OF BIRDS 



ened, and a little decurved, the downward bend increasing in 

 both mandibles towards the tip: and its surface is extensively 

 traversed by ramifications of the fifth pair of nerves, which 

 render it unusually sensitive, in beautiful adaptation to the 

 purposes for which it is employed. In connection with this 

 sensitiveness, it may be remarked that these birds are careful 

 to preserve their beak from cold, and at night are enabled to 

 bury completely its immense bulk within their body-plumage : 

 they are also frequently observed to scratch it gently with the 

 foot, as if this produced an agreeable sensation. Its struc- 

 ture is extremely delicate in the young ; and these, accord- 

 ingly, must subsist on very delicate and soft food : and it 

 is scarcely necessary to add that it does not attain its ultimate 

 magnitude for a series of years ; becoming finely coloured as 

 it approaches to maturity. The edges of both mandibles are 

 distinctly denticulated. 



The tongue, as already noticed, is a very curious instru- 

 ment, elongated and slender, and barbed not unlike a feather ; 

 its sheath giving off from the lateral margins a series of stiff 

 bristle-like appendages, directed forwards, which structure is 

 continued to the apex : the peculiar or accessory function of 

 this sort of tongue appearing to be that of touch ; it acting as 

 a kind of antenna, whereby to test the softness and ripeness 

 of fruit, and the fitness of other substances for food. That 

 the toucans also possess, however, the sense of taste in very 

 considerable perfection, will appear from a fact to be stated 

 in the course of this summary : but the dev elopement of nerv- 

 ous tissue and papillae over the beak has been erroneously 

 deemed an extension of the olfactory surface. 



These birds have the legs of mean length, and covered, as 

 are also the toes, with large scutellce : their feet are adapted 

 for hopping from bough to bough. The wings are short and 

 rounded ; and tail of moderate length, and but slightly cune- 

 ated, in the genus Rhamphastos; longer, and much graduated, 

 in the others : it is mostly held erected. The cheeks are bare ; 

 the skin of them being generally blue, and sometimes red, or 

 even green : irides most commonly pale blue : and the cloth- 

 ing plumage is of rather open texture (as in the motmots), 

 having the webs of the feathers disunited, and often glisten- 

 ing on those parts that are brightly coloured : l the accesso- 

 ry plume is flocculent and of considerable length, in some, 



1 One species, known as the curl-crested aricari, is remarkable for a curi- 

 ous modification of the feathers of its crown, which have the webs soldered 

 so as to be undistinguishable, appearing like curled and brilliantly shining 

 lamina of black sealing-wax. The intent remains to be explained. 



