128 ON THE CLASSIFICATION OF BIRDS. 
rection : by this particular structure the bird could 
bring the tips of all the four claws to touch each other, 
when grasping a small round substance, a faculty which 
no other birds, from the different position of their toes, 
can possibly possess. The annexed sketch {fig. 66'. b) of 
the foot of the little horned owl, or Scops, will illustrate 
this singular conformation of foot, which is altogether 
peculiar to such birds of the rapacious order as prey upon 
living animals. The vultures, who do not seize their 
food by their talons, have no occasion for such a foot, 
and their toes are consequently placed in the orthnary 
direction. 
CHAP. IV. 
THE SAME SUBJECT CONTINUED. ON THE DIFFERENT MODIFI- 
CATIONS OP PERCHING, CLIMBING, WADING, AND SWIMMING 
FEET. THE VOICE AND NESTS OF BIRDS. 
(116.) A pp.RCHiNG, or insessoriiil foot, for the reasons 
already stated, is pre-eminently typical of this member 
in the class of birds. Feet of this form are adapted 
both for walking upon the ground and clinging to 
branches ; tlius uniting the properties both of the 
grasping and the walking foot, hereafter defined. The 
three anterior toes are not only ilirected forwards, but 
those two of them which are on the sides have no power 
of being turned in a different direction to the middle toe, 
and this constitutes tlieir essential difference from the rap- 
torial structure. Nevertheless, it by no means follows 
tliat all birds, having three toes directed completely 
forward, and one backward, belong to the Perchers. 
The definition we have already given of the orders of 
birds (14.) will have informed the student, that the 
Rasores, the Grallatorcs, and the Natutores, notivith- 
