Forest Preserve District of Cook County, Illinois
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Animal Hands
Nature Bulletin No. 611  October 1, 1960
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
David H. Thompson, Senior Naturalist

ANIMAL HANDS
Muddy footprints shaped like babies' hands can be seen on almost every trash barrel in our forest preserve picnic areas. These are made by raccoons which come at night to eat discarded sandwiches, chicken bones and other food scraps. The hind feet as well as the front feet of the coon are built like hands and that its front foot, especially in mud or soft snow, leaves a print of the palm with four spread fingers and a thumb. The track of the hind foot is longer with a definite heal. The coon feels for fish, crawfish, frogs and snails along the water's edge, scrubbing each thoroughly before eating. Full of curiosity and mischief, a pet coon quickly learns to unlatch doors, play with small objects and pick people's pockets.

The human hand is a marvelous mechanism, the most perfectly developed in the animal kingdom for all-round uses. It has the strength to handle a sledge hammer or the delicacy of touch of the eye surgeon or watchmaker. The flexible, sensitive fingers can perform extremely precise, complicated tasks. We are astonished at the flying fingers of the expert typist or at the rippling notes of a Van Cliburn at the piano. Man takes pride in his brain but without such a hand to do its bidding he would not have gone far.

The feet of all mammals are built on the same general plan and the hand of man is typical. In the wrist which connects the hand to the forearm are eight small bones in two rows called carpels. The five long bones of the palm are the metacarpals. Attached to these are the five digits -- the thumb with two bones and each of the four fingers with three. All of these bones are bound together with tough flexible ligaments. The muscles that move the hand -- more than 30 pairs of them -- are mostly in the forearm and are attached by long tendons to the different joints. Without our thumb, which can touch the tip of each of the four fingers to form a vise, it would be very awkward to hold a pencil or eat with a fork.

Try matching up your hand, bone for bone, by feeling the front paw of a dog or cat. Both walk and run on their fingers and ball of the hand. The thumb is mounted higher and does not leave a track on the ground. The cat, unlike the dog, is able to sheathe its sharp hooked claws by doubling back the two end joints of its toes.

The feet of the opossum -- all four of them -- look more like human hands than those of any local animal. Their star-shaped tracks in snow are unmistakable. After the young leave their mother's pouch, they ride for a while on her back with their tiny fists clenched in her shaggy fur.

In some animals the fundamental pattern of the hand has been remodeled for special uses. The wing of the bat is a membrane of skin stretched over the bones of the arm, hand and leg like the covering of a kite. The slender elongated bones of all four fingers are present but the thumb is merely a clinging hook. The powerful hand of the mole with its five large claws is specially suited for burrowing. The paddle-like flippers of the whale shows no sign of fingers on the outside. Deep inside, however, are all the bones of the arm and the five digits of the hand.

The front hoof of the horse corresponds to our middle finger nail. The other fingers were sacrificed for greater speed. The fossil history of the horse, which is very complete, shows that it started out in America as a dog-sized animal with five tiny hoofs on each foot.

Man learned to count on his fingers. Imagine how different our arithmetic would have been with six fingers on each hand.


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