AVES. 



351 



In the Ostrich the feathers have no accessory 

 plume : in the Rhea it is represented by a tuft 

 of down ; in the Emeu, on the contrary, the 

 accessory plume equals the original feather, so 

 that the quill supports two shafts ; and in the 

 Cassowary, besides the double feather, there 

 is also a second accessory plume, so that 

 the quill supports three distinct shafts and 

 vanes. 



The feathers vary in form in different parts 

 of the bird according to their functions, and 

 afford zoological characters for the distinction 

 of species; they have, therefore, received in 

 Ornithology distinct names. Those which 

 surround or cover the external opening of the 

 ear are termed * auriculars.' Those which 

 lie above the scapula and humerus are 

 called the ' scapulars.' The small feathers 

 which lie in several rows upon the bones of 

 the antibrachmm are called the * lesser coverts ' 

 (tectrices primte). Those which line the under 

 or inner side of the wings are the ( under 

 coverts.' The feathers which lie immediately 

 over the quill-feathers are the * greater coverts ' 

 (tectrices secundte). The largest quill-feathers 

 of the wing, which arise from the bones of 

 the hand, are termed ' primaries' (primores). 

 Those which rise from the ulna, towards its 

 distal end, are the ' secondaries' (secondaria). 

 Those which are attached to its proximal ex- 

 tremity are the ' tertiaries' (tertiaria). These 

 in some birds, as the Woodcock and Snipe, 

 are so long as to give them the appearance, 

 when flying, of having four wings. The 

 quill-feathers which grow from the phalanx, 

 representing the thumb, form what is termed 

 the bastard wing (alula spuria). 



In considering the structures which deter- 

 mine the powers of flight in different birds, 

 it is necessary to take into account the structure, 

 forms, and proportions of the wing-feathers, 

 as well as the development of the bones and 

 muscles which support and move them ; as 

 much depends upon the mechanical advantages 

 resulting from the shape and texture of the 

 expanded wing. When the primary quill- 

 feathers gradually increase in length as they 

 are situated nearer the extremity of the pinion, 

 they give rise to the acuminated form of wing, 

 as in the true Falcons, in which the second 

 primary is the longest. In the Hawks the 

 wing is of a less advantageous form, in con- 

 sequence of the fourth primary being the 

 longest; when the primaries gradually decrease 

 in length towards the end of the pinion, they 

 give rise to a short rounded form of wing, 

 such as characterizes the Gallinaceous Order; 

 in which, although the pectoral muscles are 

 immensely developed in order to counteract 

 the disadvantage resulting from the disposition 

 of the primaries, yet they are only able, in 

 consequence of the form of the wing, to carry 

 the bird rapidly forward for a short distance, 

 and that with an exertion and vibratory noise 

 well known to every sportsman. 



The texture of the quill-feathers has also a 

 material effect on the powers of flight. In 

 the Falcons each primary quill-feather is 

 elongated, narrow, and gradually tapers to a 

 point; the webs are entire, and the barbs 



Fig. 179. 



closely and firmly connected together.* In 

 the Owls the plumage is loose and soft, and 

 the outer edge of the primaries is serrated ; 

 so that, while they are debarred from a rapid 

 flight, which would be dangerous in the gloom 

 in which they go abroad, they are enabled, by 

 the same mechanism, to wing their way without 

 noise, and steal unheard upon their prey. 



Development of feathers. The first covering 

 of the bird is a partial and temporary one, 

 consisting of fasciculi of long filaments of 

 down, which on their first appearance are en- 

 veloped in a thin sheath, but this soon crumbles 

 away after being exposed to the atmosphere. 

 The down-fasciculi, which diverge each from 

 a small quill, are succeeded by the fea- 

 thers, which they guide, as it were, through 

 the skin : and after the first plumage, at each 

 succeeding moult, the old feathers serve as 

 the gubernacula to those which are to follow. 

 It is to be observed that feathers do not grow 

 equally from every part of a surface of a bird ; 

 they are not developed, for example, at those 

 parts which are subject to friction from the 

 movements of the wings and legs. They 

 first appear in clumps upon those parts of the 

 skin which is least affected by the pressure of 

 superincumbent parts, or the movement of the 

 parts beneath, as upon the head, along the 

 spine, upon the exterior surface of the extre- 

 mities, at the intervals of the joints on either 

 side the projecting sternum, and at the sides 

 of the abdomen. 



The matrix, or organ by 

 which the perfect feather is 

 produced, has the form of an 

 elongated cylindrical cone, 

 and consists of a capsule, a 

 bulb, and intermediate mem- 

 branes which mould the secre- 

 tion of the bulb into its ap- 

 propriate form. The matrix 

 is at first an extremely minute 

 cone, attached by a filamen- 

 tary process to a follicle or 

 papilla of the skin ; but it is 

 not a development of that 

 part, being of a different 

 structure and adhering to it 

 by a small part only of ts 

 circumference. The matrix 

 progressively increases in 

 length ; its base sinking deep- 

 ly into the corium, and ac- 

 quiring a more extended con- 

 nection by enlarged vessels 

 and nerves, while its apex 

 protrudes to a greater or less 

 extent from the surface of the 

 integument, when the cap- 

 sule drops off to give passage ^ . . f 



. . 7 " & Matrix of a grow- 

 to the feather wh ich it incloses, ing Feather, with 



and the formation of which the Capsule laid 

 has, in the meanwhile, been open. 



* Of so much consequence are the quill-feathers 

 to the Falcons, that when any of them are broken 

 the flight is injured and the falconers find it ne- 

 cessary to repair them ; for this purpose they are 

 always provided with perfect pinion and tail fea- 

 thers, regularly numbered. 



