evolution has
been controlled by the same "eternal, iron laws" as the development of
any other body--the laws of heredity and adaptation.

WILLIAM HARVEY

On the Motion of the Heart and Blood

William Harvey, the discoverer of the circulation of the blood, was
born at Folkestone, England, on April 1, 1578. After graduating
from Caius College, Cambridge, he studied at Padua, where he had
the celebrated anatomist, Fabricius of Aquapendente, for his
master. In 1615 he was elected Lumleian lecturer at the College of
Physicians, and three years later was appointed physician
extraordinary to King James I. In 1628, twelve years after his
first statement of it in his lectures, he published at Frankfurt,
in Latin, "An Anatomical Disquisition on the Motion of the Heart
and Blood," in which he maintained that there is a circulation of
the blood. Moreover, he distinguished between the pulmonary
circulation, from the right side of the heart to the left through
the lungs, and the systemic circulation from the left side of the
heart to the right through the rest of the body. Further, he
maintained that it was the office of the heart to maintain this
circulation by its alternate _diastole_ (expansion) and _systole_
(contraction) throughout life. This discovery was, says Sir John
Simon, the most important ever made in physiological science. It is
recorded that after his publication of it Harvey lost most of his
practice. Harvey died on June 3, 1657.

_I.--Motions of the Heart in Living Animals_

When first I gave my mind to vivisections as a means of discovering the
motions and uses of the heart, I found the task so truly arduous that I
was almost tempted to think, with Fracastorius, that the motion of the
heart was only to be comprehended by God. For I could neither rightly
perceive at first when the systole and when the diastole took place, nor
when and where dilation and contraction occurred, by reason of the
rapidity of the motion, which, in many animals, is accomplished in the
twinkling of an eye, coming and going like a flash of lightning. At
length it appeared that these things happen together or at the same
instant: the tension of the heart, the pulse of its apex, which is felt
externally by its striking against the chest, the thickening of its
walls, and the forcible expulsion of the blood it contains by the
constri