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Janice Pleban, age 9, of Trumbull, Connecticut, for her question:

Why does an octopus have three hearts?

A horse can run like the wind because he has a mighty strong heart. Dogs need a strong heart to keep on the go. These busy animals have hearts like ours    and one per person is enough to do the work. The octopus, however, is not a very busy character. Down there on the floor of the sea, he takes his time    tiptoeing around, gliding and. floating. You would think that he needs only one small heart to keep him going. So it's very surprising to learn that the octopus has three hearts.

Many people think that all nature's animals have ,just one heart apiece. But a great many creatures have hearts that are very different from ours and a lot of them have more than one. For example, the shy little earthworm has 10 tiny hearts to pump his blood around his body. The octopus and his kinfolk have three little hearts to keep the blood circulating. Naturally, there is a reason why they need more than one.

Their little hearts are very simple and it takes several of them to do all the work done by one heart like yours. Actually the human heart is four hearts in one. Its thick wall is a mighty muscle. Inside there are four little rooms, or chambers. Down the middle is a sturdy wall that seals an upstairs and a downstairs chamber on each side. Valves and trapdoors connect the heart to large tubes that carry the blood in and out. All the parts work together to do four different fobs. They collect fresh blood from the lungs    and collect used blood that has circulated around the body. They pump used blood to the lungs for fresh oxygen    and pump fresh blood around the body again.

An octopus also must refresh his blood and keep it circulating. But he cannot breathe air because he lives under water. So instead of lungs he has a pair of feather gills, deep inside his body. Gills work somewhat like lungs but they must take their oxygen from the water. If the octopus had a four chambered heart, he would need only one to keep his blood circulating. But instead he has three simple little hearts to do the job.

One is placed near each gill. These two collect used blood. Then each pumps this blood through one of the gills. There it gives up its waste carbon dioxide and  takes fresh oxygen. This fresh blood goes to the third heart. And this one pumps it into a network of branching blood vessels. This network leads the used blood back to the two little gill hearts. Back it goes to the gills and on to the non stop circulation through the body.

The wonderful human heart does all these chores together. With a soft lub dub, it pumps and pauses in double beats. Each pump sends used blood from the right side to the lungs    and fresh blood from the left side to pulse around the body. As it pauses, used blood returns and fills the right side    and fresh blood from the lungs flows in to fill the chambers on the left side. Your one heart works better than the three separate hearts in an octopus..

 

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