Chapter IV, in which he describes the movements of the auricles and ventricles, is a model of accurate description, to which little has since been added.

It is interesting to note that he mentions what is probably auricular fibrillation.

He says: "After the heart had ceased pulsating an undulation or palpitation remained in the blood itself which was contained in the right auricle, this being observed so long as it was imbued with heat and spirit." He recognized too the importance of the auricles as the first to move and the last to die.

The accuracy and vividness of Harvey's description of the motion of the heart have been appreciated by generations of physiologists.

Having grasped this first essential fact, that the heart was an organ for the propulsion of blood, he takes up in Chapters VI and VII the question of the conveyance of the blood from the right side of the heart to the left.