EXTERNAL ANATOMY. BILL. 
65 
That the humming birds, and all those which suck the 
contents of flowers, should have a bill so much length- 
ened, is owing to the nature of their food, which re- 
quires the faculty of iirobing the bottom of those long 
tubular flowers of the natural order of Bignimiacce, with 
which the forests of tropical regions abound; this struc- 
ture, in fact, is as necessary to them as an elongated mouth 
is to bees, which feed upon, and have to reach, the very 
same substance. It may here be observed, and laid 
down as a general rule, that as a depressed bill always 
indicates weakness, so one that is compressed on its sides, 
(that is, whose length is always greater than its breadth), 
indicates strength. No better proof of this position can be 
adduced than the genera Platyrhyncku« and Mfgalophus, 
as examples of the first of these forms; and that of the 
crows or the parrots, as examples of tlie second. When, 
however, the bill is not only short, but so thick as to 
become almost round or cylindrical, we have exam- 
ples of the greatest strength with which Nature has 
endowed the mouth of birds. No group in the orni- 
thological circle exhibits this powerful structure so much 
as that of the Fringillidce, where the bill is short, and 
nearly conic ; both mandibles are equally thick, and 
when closed, their height and breadth are nearly the 
same. In many of the finches (as in the sub-genera 
Amadina, Coccothramtes, &c.), the thickness of the bill 
at its base, in comparison to the size of the head, is 
enormous : but in the Loxia 
Ostrina of Vieillot {fig. 32.), 
a rare and most extraordinary 
bird from Western Africa, the 
bill is not much inferior to 
the size of the head. It is 
well known that all these 
“ hard-billed” birds, as the 
old writers aptly called them, feed entirely upon seeds 
and nuts ; and the harder these are, the stronger are the 
bills of such species as are appointed to derive nourish- 
ment from the different sorts. Whenever an insectivorous, 
