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arteries, whose walls more dense than the veins yielded to the pressure. If he had been content to reason only, he could never have shewn the error of the Galenic doctrine. It was by experiments on living animals that the truth was made clear to the mind of Harvey. Let us quote his words, and I use the translation of Willis, published for the Sydenham Society. "In the first place then, when the chest of a living animal is laid open and the capsule that immediately surrounds the heart is slit up or removed, the organ is seen now to move, now to be at rest; there is a time when it moves, and a time when it is motionless." "These things e more obvious in the colder animals, such as toads, frogs, serpents, small fishes, crabs, shrimps, snails, and shell fish. They also become more distinct in warm blooded animals, such as the dog and hog, if they be attentively noticed, when the heart begins to flag, to move more slowly, and, as it were to die; the movements then become slower and rarer, the pauses longer, by which it is made more easy to perceive
