Thomas of Chatimpre and Vincent of Beauvais. Blessed Albertus wrote seven books on plants and twenty-six books on animals. Of the latter works, some are based on original research, while others contain many new and accurate observations which to-day are becoming more and more highly ap- preciated by scientists.
The second period began with the Belgian anato- mist Andreas VesaliiLs, b. at Brussels, 1 January, 1.515. Vesalius was the first who dared to oppose energetically the authority of Galen in certain ana- tomical questions and to insist that in such matters not the method of interpretation, but that of dis- section and of personal observation alone could lead to truth and progress. In 1537 Vesalius was made Doctor of Medicine in the University of Padua, where, during the following five years "he conducted the public dissections. At the end of this time he pub- lished an illustrated folio on the structure of the human body, "Fabrica humani corporis", which appeared at Basle in 1543. In this famous volume Vesalius corrected many errors of Galen, introduced his new method of dissection and experiment in the study of anatomy, and tlius became the founder of modern anatomy. The attempt of Vesalius to over- tlirow traditional metliods met with much encourage- ment, but much more opposition, apparently, for a year after the publication of his "Fabrica" he accepted the post of court physician offered to him by Charles V. In 1563 he made a pilgrimage to Jerusalem, and on his way back, in 1564, died on the island of Zante.
One of the greatest successors of Vesalius was William Harvey, b. at Folkestone, England, in 1578. Harvey studied medicine at Padua at the time when the Tuscan Fabrieius ab Aquapendente (1.537-1619) held the chair of anatomy anci wrote his exposition of the Galenic doctrine concerning the circulation of the blood. In 1604 he joined the Royal College of Physicians in London. Later on he became physician to Charles I, and died 3 June. 1667. The importance of Harvey's work for biology consists in the demonstration of the true circulation of the blood through the arteries and veins. This demon- stration, which he developed for the first time in his anatomical lectures at the Royal College in the year 1615, was published in 1628 under the title of "Exercitatio de cordis motu". Together with the discovery of the lymphatics by Aselli (1623), to which it gave rise, it constitutes the beginning of modern physiology whose existence and develop- ment is in no small degree due to the purely ex- perimental method definitely introduced bv Harvey.
Meanwhile Galileo Galilei had made his discoveries in physics, and it was not long before these dis- coveries began to exercise their influence upon bio- logical studies. It was especially Giovanni Alphonso Borelli, b. at Naples, 28 Januarj-, 1608, who suc- cessfully attacked the mechanical problems sug- gested by muscular movement. When professor of mathematics at the University of Pisa he became acquainted with Marcello Malpighi. of Bologna, through whom he became interested in anatomical studies, and soon set about preparing a treatise on animal motion, "De motu animalium", which was the first of the great contributions to physical physi- ologj'. This influential work appeared in 1680, shortly after the death of its author. While Borelli was still at work on his "De motu", another anato- mist, Nicolaus Stenson, or Steno (1638-86) de- veloped in the same line, together with his friend Malpighi, the special physiology of glands and tissues. Steno, a convert from Lutheranism to Catholicism, wao professor of anatomy in Copenhagen, his native city, and afterwards a priest and bishop in Hanover. He was one of the first to recognize the imporiance of the rising science of chemistrj-, although his at-
tention was too much occupied with the new science of geology, which he had founded, to leave him much time for other investigations. The introduction of chemical methods in biological studies had already been accomplished by Jan Baptista van Helmont, b. at Brussels in 1577, who in his turn was greatly influenced by the fantastic pilgrim Paracelsus (Theophrastus Bombast von Hohenheim), and through him by the Benedictine monk Basil Valen- tine. The latter lived about the time of Johannes Gu- tenberg and is known as the last alchemist and the first chemist.
Van Helmont's important work, "Ortus medicinte" appeared four years after his death, but it was the first of its kind and, like Borelli's book, exercised an important influence on future investigations. The most valuable idea of the "Ortus medicinse" is the explanation of digestion by fermentative proc- esses. Perhaps the most influential of van Helmont's intellectual descendants was Franz de la Boe, or Franciscus Sylvius, professor of medicine at Leyden from 1058 till his death in 1672. Sylvius was the teacher of such brilliant men as Steno and Regner de Graaf, to whom we owe several important biological discoveries. Without making any great discoveries himself he succeeded in directing the attention of physiologists, much more than van Helmont had done, to the importance of chemistry for the solution of biological problems. ThiLs he became the founder of the iatro-chemical school which, in opposition to the iatro-physical school of Borelli's followers, attempted to explain all vital processes bj' mere chemistry.
The work of Malpighi both closes this second period in the history of biology and reaches far out into modern times. Marcello Malpighi was born at Crevalcore near Bologna, in 1628, the year in which Harvey published his essay on the circulation of the blood. He did more for the general advancement of biologj' than any other scientist since the days of Vesalius. With the Englishman Xehemiah Grew, he laid the foundation of vegetable morphologj'. His work on the silkworm argues him a remarkable anatomist, and his description of the development of the hen's egg entitles him to be considered the first embrj'ologist . But his most important work con- sists in the discovery of the capillaries and the air- sacs in the lungs, and of the structure of glands and glandular organs. During the greater part of his splendid career ilalpighi was professor of medicine at Bologna. In 1691 Pope Innocent XII called him to Rome to be the papal physician; Malpighi com- plied with the invitation, and died at Rome, 28 No- vember, 1694. A great part of Malpighi's success was due to the fact that the microscope, one of the most important scientific instruments of modern times, had just been invented.
It is noteworthy that nearlj' all the great pioneers of biological progress during this second period were devoted Catholics. The Church never hampered these great scientists, so long as they proceeded h}- way of exact demonstration, and kept within their own province, but left them perfectly free in their investigations. The exceptional ecclesiastics who assumed an unfriendly attitude towards scientific enlightenment may well be excused when we con- sider, as a mere physiological fact, how deeply in- herited conceptions take root in the individual mind, and, moreover, how easily any novel idea may be misinterpreted as conflicting with religious truth. But the most determined opponents of biological innovations wer^ indeed not ecclesiastics at all. but professors of biology who found it hard to give up the ancient traditions of their lifelong study.
Third period. — Of Linnaeus (Karl von Linnd) it has been said that he found natural science a chaos and left it a cosmos. The son of a Protestant mini.s-