Servetus believed the umbilical arteries to be _efferent_ channels of the vital spirit of the mother to the heart of the fœtus. He at the same time, doubtless, saw the umbilical veins as the channels by which material for its growth and nutrition was brought from the mother to be distributed by the venous system proceeding from the liver and vena cava, in conformity with the physiological views of his age. Servetus did not think of the fœtal heart save as the passive recipient of life. He never heard its rapid tick tack, nor dreamt of it any more than he did of the heart of the adult as the agent in the general distribution of the blood in a great circle from arteries to veins, from veins to arteries, unbroken in the embryo, but complicated when independent life is assumed by the necessary passage through the lungs. Imperfectly, incompletely, therefore, as the great function of the circulation is conceived by Servetus, his account of so much of it as belongs to the pulmonary system is all his own and an immense advance on aught that had been imagined before. Had his ‘Restoration of Christianity’ been suffered to get abroad in the world and into the hands of anatomists, we can hardly imagine that the immortality which now attaches so truly and deservedly to the great name of Harvey would have been reserved for him. But save to a few theologians, who gave no heed to his physiological speculations, Servetus’s book remained unknown in the republic of letters, for more than a century after it had fallen from the press--no naturalist had seen it during all that time. So effectually had it been hunted out and made away with, that of the thousand copies printed, two only, as we have seen, are now known to survive. The ‘Christianismi Restitutio’ of Michael Servetus, consequently, never influenced either speculation or discovery in connection with the circulation of the blood. But reading the book as we are now suffered to do, let us not overlook in its author the Physiological Genius of his age. Who shall say what amount of influence the ‘Restoration of Christianity’ might have had upon both Science and Religion had it been suffered to see the light! For it is not the possession only, but the pursuit of truth that truly ennobles man; and in Servetus’s incomplete induction in the sphere of physics we see the path fairly entered on that has given to modern science all its triumphs. Nor pause we here: in the domain of letters and criticism, he is nowise less in advance of his age than in physiology. Who among biblical scholars before Servetus had seen the applicability of so much that is said in the Psalms and prophetical books of the Jewish Scriptures to men and events contemporaneous with, when they had not preceded, the times in which their authors lived? Servetus’s contemporaries among the Reformers without exception set out from the _letter_ of the New Testament as the source of their faith, the warrant for the conclusions they built upon its text.