Page:The Harveian oration, 1875 (IA b22314611).pdf/23

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like a bundle of twigs bulging in the centre, whereas the fibres acting together, constringe the heart and make it tense and that (as Bauhin and Riolan asserted) it has four motions distinct in time and place—two proper to the auricles, two to the ventricles.

I must not stop to notice the multitude of curious facts by which Harvey illustrates this division of his subject; nor what use he makes of the magnifying glass to watch the heart's beat in such creatures as slugs and snails, crabs, wasps and flies, and that convenient transparent shrimp taken in the Thames and in the sea, in which the heart is seen as through a window; nor again, those observations, so minute and exact, relating to the first appearance in the embryo of the "pulsating drop of blood," and gradual development of the heart.

From the motions of the heart Harvey leads us on to those of the arteries, as seen in living animals. He tells us that at the moment the heart contracts and strikes the breast (the heart’s systole), the arteries are dilated, and yield a pulse (their diastole); and that this happens with the right ventricle and pulmonary artery equally with the

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