OSTRICH PLUMES. 379 



tlie direction of the convex and concave sides of the feathers ; con- 

 sequently they present considerable resistance to being bent out of their 

 plane, although readily yielding to any force acting upon them in the 

 direction of the line of the stem. 



The barbules are given off from either sides of the barbs, and are 

 sometimes similarly barbed themselves, as may be seen in the barbules of 

 the long feathers of the peacock's tail. 



The barbules are commonly short and close-set, and curved in con- 

 trary directions, so that two adjoining series of barbules interlock toge- 

 ther, and form the mechanism by which the barbs are compacted into 

 the close and resisting vane of the quill, or " feather," properly so called. 

 When the barbules are long and loose, they characterise that form of 

 the feather which is properly called a " plume," and such are the most 

 valuable products of the plumage of birds in a. commercial point of 

 view ; as, e. g. the plumes of the ostrich. 



The lower barbs in every kind of feather are usually loose, forming 

 the down, which is increased, in most birds, by what is called the "acces- 

 sory plume." This is usually a small downy tuft, but varies in different 

 species, and even in the feathers of different parts of the body of the 

 same bird. The value of the feathers, for bed-stuffing depends upon the 

 proportion of loose soft down that enters into their composition ; and as 

 the " accessory plume " in the body feathers of the swans, geese and 

 ducks, is almost as long as the feather from which it springs, hence 

 arises the commercial value of the feathers of these aquatic birds. 



In the development of plumage, the first covering of the bird is a 

 temporary one, consisting of bundles of long, loosely-barbed filaments, 

 which diverge from a small quill, and on their first appearance are enve- 

 loped in a thin sheath, which soon crumbles away after being exposed to 

 the atmosphere. These down-feathers are succeeded by the true feathers ; 

 to which they bear the same relation as wool does to hair, or the tempo- 

 rary to the permanent teeth. In most birds a certain proportion of the 

 down-feathers is retained with the true feathers, and this projjortion is 

 usually greatest in the aquatic birds* 



Of the various kinds of feathers employed as plumes for head dresses, 

 the most important are those of the ostrich, the Struthio camelus, which 

 belongs to a peculiarly African genus of the great wingless birds. If 

 the ostrich ever slips into Asia, it is only a little way into the Arabian 

 side of the Isthmus of Suez. 



The feathers on the body of the male bird are black, but on the female 

 dusky ; those of the wings and tail are white, sometimes marked with 

 black. The ornamental wings are furnished with loose and flexible plumes. 

 The elegance of these feathers, arising from their slender stems and the 

 disunited barbs has occasioned them to be prized in all ages ; and as 

 they still constitute a valuable article of commerce, there is small chance of 



* Professor Owen's Lecture on Raw Materials from the Animal Kingdom. 



