PLUMAGE OF BIRDS. SKELETON. 363 



case with the wing-feathers of the Eagle and the Crow. There 

 are others, again, in which the vanes and their barbs are long and 

 flexible, and do not hook into each other, so that they have an 

 extreme degree of lightness and softness; feathers of this kind 

 are met with in the wings and tail of the Ostrich. And lastly, 

 there are some which resemble mere down^ the laminae being very 

 narrow and totally unconnected ; such are those, obtained from 

 the Adjutant, which are much valued as articles of ladies' dress, 

 and are known under the name of Maraboo feathers. The colours 

 of feathers are exceedingly varied, and often surpass in beauty 

 and sptendour those of the most beautiful flowers, or the most 

 brilliant stones. The plumage of the female is generally less 

 varied than that of the males ; and the young birds rarely exhibit 

 the colours that they will preserve all their lives; they often 

 change for two or three years successively ; and sometimes the 

 adult has a summer plumage quite different from its winter one. 

 Among aquatic birds the feathers are provided with a fatty 

 matter, which renders them impermeable to water ; this enables 

 them to preserve the skin of the animal from contact with the 

 liquid in which it is partly plunged. 



326. The skeleton which determines the general form of Birds, 

 and which is at the same time one of the most important parts 

 of its apparatus for locomotion, is composed of nearly the same 

 elements as among the Mammalia ; but the form and arrange- 

 ment of many of its bones are different ; and with an equal 

 volume they are also lighter, most of them being hollowed out 

 into numerous small cavities filled with air. The head of these 

 animals (Fig. 178) is generally small ; when young the skull is 

 composed of the same bones as in the Mammalia; (viz. two 

 frontal bones, two parietal, one occipital, two temporal, one 

 sphenoid, and one ethmoid) ; but all these parts are firmly fixed 

 together at a very early age ; and then cease to be recognizable. 

 The face is almost entirely formed by the jaws, which are much 

 elongated, and which, being destined to constitute the principal 

 organ of prehension, vary much in size and form according to the 

 nature of the objects which the bird will require to seize. The 

 upper mandible is so united to the frontal bone, as to preserve 



