156 
AVES. 
The bony tail is very short, [and consists in most instances of nine vertebrae, the 
three last of which are commonly anchylosed into a plough- share form, and are gene- 
rally collectively styled the coccyx] , but has a range of strong feathers, which, when 
spread out, assist in supporting the bird : their number is ordinarily twelve ; sometimes 
fourteen, and in many of the GallmacecR eighteen ; [in some few genera, as the 
Grebes, Nandou, &c., these are wanting altogether ; a single Humming-bird (Trochilus 
enicurus) possesses only six ; the Ani eight ; the rest of the Humming-birds, and 
various others, ten ; while the Swans present from eighteen to twenty-two. The two 
central of these feathers are implanted above the even line formed by the insertion of 
the rest, and essentially correspond to the wing-tertiaries, as the others do to the 
wing- secondaries ; the latter being in no instance moulted more than once in the year, 
the former in many instances twice : we might accordingly designate the two central 
tail feathers, which differ conspicuously from the rest in structure, uropygials. Above 
and below the tail are lengthened feathers, commonly of weak texture, known as the 
upper and under tail-coverts. 
The rest of the feathers of Birds are named from their position, as frontal, coronal, 
occipital, nuchal, dorsal or interscapulary , which together form a continuous series, apart 
from the scapalaries ; those in front of the eye are termed and the auditory aperture 
is covered by a range styled auriculars or ear-coverts : the sides of the neck and medial , 
portion of the sternal and abdominal region are at most covered with down; the>^: 
former being concealed by the lateral feathers of the fore and hind neck meeting ; 
latter by a similar junction of two distinct lateral ranges. As it is necessary that the 
warm body of a bird should be in actual contact with the eggs during incubation 
whatever down may cover the medial inferior region disappears in the females towards 
the season of propagation, even in those confined in cages, so that this bareness is not 
produced mechanically. Finally, besides various accessory tufts in different genera,l| 
some long slender feathers are situate at the base of the wing internally, which are® 
named axillaries]. 
The legs have a femur, a tibia, and a peronseum attached to the femur with a spring,' 
thlf^ 
which maintains their extension without effort on the part of the muscles. The tarsus j 
and metatarsus are represented by a single bone, terminating below in three pullies. 
Most commonly there are three toes before, and a thumb behind* ; the latter being 
sometimes deficient. In the Swifts it is directed forwards, [though half-reversible ; in 
the Moth-hunters and some others, inward, at a right angle with the axis of the body].% i 
In the yoke-footed Birds, on the contrary, the external toe and the thumb are dis-l| 
posed backwards [most usually, but sometimes (as in the Touracos and Puff-birds)U|f 
laterally : in the Trogons, the first and second toes are opposed to the third and| 
fourth ; and accordingly the longest toe, or that which corresponds to the middle one| 
in the generality of the class, is inward, instead of being outward, as in all the other 
yoke-footed groups] . The number of articulations increases in each toe, commencing 
with the thumb, which has two, and ending with the external toe, which has five. 
[The Swifts present a remarkable exception ; and it may be remarked that, in the 
Ostrich alone, only two toes are present.] 
In general, [invariably]. Birds are covered with feathers. 
sort of tegument best 
* The word iAumJ is here and subsequently used merely in a popular | thumbs of the Quadrnmana arc represented, in the class of Birds, 
sense, to signify its antagonism to the other digits : as the hinder 1 only by the tarsal spurs of many Gallinacea.—^’a. 
