Swimming foot of Coot, with lobed toes; 10. Swimming foot of Canada
Goose, with three toes webbed; 11. Swimming foot of Cormorant, with all
four toes webbed.]

"It's the heel in people, but I should think the hind toe of a bird was
its heel," said Nat doubtfully, and beginning to think he did not
understand.

"You might think so," said the Doctor; "but you would be wrong. All this
horny part that a bird stands up on is its foot. And the top of it,
nearest to the feathers, is the heel. Don't you see, when I bend the
foot _so_," continued the Doctor, as he bent the Sparrow's foot forward,
"that the top of the horny part makes a joint that stands out backward,
in the same position your heel always has? All this slender horny part
of the foot, above the roots of the toes, corresponds to the instep of
your foot, and of course the heel comes next. You must remember the name
of it--the Wise Men call it the _tarsus_."

"Then hasn't a bird got any legs, Uncle Roy, only just feet?" asked
Dodo.

"Oh! yes; legs too, with a knee-joint and a hip-joint, like ours. But
all these parts are up closer to the body, and hidden by the feathers,
so that you cannot see them."

As the Doctor said this there was a great commotion. Quick, who had been
watching the mouse hole all the while, gave a sharp bark and pounced on
something. There was a feeble squeak, and it was all over with a mouse
which had ventured too far from its hole.