122 
ON THE CLASSIFICATION OF BIRDS. 
but there is no breadth of sole, the tarsus is much more 
lengthened, and the toes, instead of being thick and 
strong, are slender and weak. These birds never climb, 
but as they sit much, and often very long, upon 
branches, it is necessary their feet should be of such a 
form as to enable them to preserve an equal hold on all 
sides : we accordingly tenn their feet graxping. Next 
come the trogons, whose toes are arranged quite dif- 
ferently, although, like the last mentioned groups, diey 
have two before and two behind, but the latter are 
perfectly posterior; and as they are altogetlier inca- 
pable, from the manner of their insertion, of being 
moved from their ordinary position, the trogons might 
be termed the only birds whose toes are absolutely in 
pairs : they are, perhaps, the most sedentary birds in 
creation, and hence their feet, which are also the 
weakest, seem to be' constructed for the sole purpose of 
sitting still. We shall retain the appellation of Grexsoriul 
to this form, the characters of which are, in addition 
to the toes being disposed in pairs, that the two anterior 
are by far the longest, and are connected together to 
nearly half their length ; the two posterior being sepa- 
rated, and the outer one nearly half the length of the 
inner. 
(112.) The true A’coiworM foot is seen only in the 
woodpeckers. We must still consider these birds in 
the same light as we have done the parrots, that is in 
having the toes placed in pairs ; for although the base 
of the outennost seems to be on the same level with 
that of the two which are anterior, this outer toe can- 
not be brought even half way forward, at least in any 
of the species we have examined in a fresh state with 
out violence ; and, indeed, this latter faculty is \iot at 
all required by Ac habits of these birds, for they never 
use the foot either m feeding or in grasping. On flying 
from one tree to another, the woodpecker generally 
ahghts upon the upright stem, rather than upon an 
horizontal branch, and immediately begins, in a per- 
pendicular attitude, to explore the barkrand detect the 
