to pound it quietly and alternately with their fore-feet;
their toes being spread out and claws slightly protruded,
precisely as when sucking their mother. That it is the same
movement is clearly shown by their often at the same time
taking a bit of the shawl into their mouths and sucking it;
generally closing their eyes and purring from delight.
This curious movement is commonly excited only in association with
the sensation of a warm soft surface; but I have seen an old cat,
when pleased by having its back scratched, pounding the air
with its feet in the same manner; so that this action has almost
become the expression of a pleasurable sensation.


[16]"Dr. Darwin, `Zoonomia,' 1794, vol. i. p. 160. I find that
the fact of cats protruding their feet when pleased is also noticed
(p. 151) in this work.

Having referred to the act of sucking, I may add that this complex movement,
as well as the alternate protrusion of the fore-feet, are reflex actions;
for they are performed if a finger moistened with milk is placed
in the mouth of a puppy, the front part of whose brain has been
removed.[17] It has recently been stated in France, that the action
of sucking is excited solely through the sense of smell, so that
if the olfactory nerves of a puppy are destroyed, it never sucks.
In like manner the wonderful power which a chicken possesses only a few
hours after being hatched, of picking up small particles of food,
seems to be started into action through the sense of hearing;
for with chickens hatched by artificial heat, a good observer found
that "making a noise with the finger-nail against a board, in imitation
of the hen-mother, first taught them to peck at their meat."[18]