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The Greatest Mystery of Whales The whale is a mammalwarm-blooded, air-breathing, giving birth to its young alive1, sucking themand, like all mammals, originated on land. There are many signs of this. ___D_1____ from flippers, used for steering and stability, are traces of feet. Immense strength is built into the great body of the big whales, and in fact most of a whales body is one gigantic muscle. The blue whales pulling __A__2____ has been estimated at 400 horsepower. One specimen was reported to have __C__3___ a whaling vessel for seven hours at the __B__4____ of eight knots. An enraged whale will attack a ship. A famous __C__5____ of this was the fate of whaler Essex, which was sunk ___6__A_ South America early in the last century. More recently, steel ships have had their plates buckled2 in the same way. Sperm whales were known to __B___7____ the old-time whaleboats in their jaws and crush them. The greatest mystery of whales is their diving ability. The sperm whale can ____8___C_ the bottom for his favourite food, the octopus. _A__9___ he is known to go as far down as 3,200 feet, where the pressure is 1,400 pounds, to the square inch. Doing ____10__A__ he will remain submerged as long as one hour. Two feats are involved in this: storing up enough _B___11____ and withstanding the great change in pressure. Just __C__12___ he does it scientists have not determined. It is believed that some of the oxygen is stored in a special system of blood vessels, rather than just held3 in the lungs. And __A__13____ that a special kind of oil in his head is some sort of compensating mechanism that automatically adjusts the internal pressure of his body. But_C____14_____ you cant bring a live whale4 into the laboratory for study, no one __B___15__ just how these things work. | 
