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arteries not only in man, but in all animals that have hearts; and, further, by frequent appeals to vivisection and constant ocular inspection, to investigate and endeavour to find out the truth.” He nowhere gives a complete list of the animals he employs. He mentions, as it were incidentally, dogs, hogs, sheep, birds, fish, eels, snakes, lizards, toads, frogs, crabs, shrimps, snails, shell-fish, bees, wasps, hornets, flies. He laid all the kingdom of Nature under contribution, and sacrificed hecatombs of victims. He went still further. Directed to it by a remark of Aristotle, he commenced the study of the development of the fowl in the egg, and also examined the foetus in man and animals.
At first he tells us that all was obscure, and he found the task so difficult that he was tempted to think with Fracastorius “that the motion of the heart was only to be comprehended by God.” But at length, by constant looking and watching, the thing became clear. He disentangled one movement from another, arranged them in
