Her work entitled Liber Simplicis Medicinæ, which deals with what in the Saint's time was called "simples"—for the belief was then current that each plant or herb was or provided a specific for some disease—contains accounts of many plants used in materia medica, as well as statements of their importance in therapeutics. Her descriptions often indicate an observer of exceptionally keen perception and one whose knowledge of science was far in advance of her epoch. The same observations may be made respecting Hildegard 's work, Liber Compositæ Medicinæ, in which she treats of the causes, signs and treatment of diseases.[188]

Still more remarkable, in many respects, is a treatise in nine books, entitled Physica or Liber Subtilitatum Diversarum Naturarum Creaturarum, which, among other things, treats of the various elements, of plants, trees, minerals, fish, birds, quadrupeds, and of the manner in which they may be of service to man. Of so great importance was this book considered that several editions of it were printed as early as the sixteenth century. No less an authority than the late Rudolph Virchow, the founder of cellular pathology, characterizes it as an early materia medica, curiously complete, considering the age to which it belongs.[189] And Hæser, in his history of medicine, directs attention to the historical value of the book, declaring it to be "an independent German treatise, based chiefly on popular experience."

Dr. F. A. Reuss, of the University of Würtzburg, at the conclusion of his Prolegomena to the Physica published in Migne's Patrologia, expresses himself as follows regarding the writings and medical knowledge of the illustrious abbess of Bingen: "Among all the saintly religieuses who, during the Middle Ages, practiced medicine or wrote treatises on it, the first, without contradiction, is Hildegard. According to the monk Theodoric, who was an eye witness, she had to so high a degree the gift of healing that no sick person had recourse to her without being restored to health. There is among the books of this prophetic virgin a work which treats of physics and medicine. Its title is De Natura Nominis Elementorum Diversarumque Creaturarum, and it embodies, as the same Theodoric fully explains, the secrets of nature which were revealed to the saint by the prophetic spirit. All who wish to write the history of the medical and natural sciences should read this book, in which the holy virgin, initiated into all the secrets of nature which were then known, and having received special assistance from above, thoroughly examines and scrutinizes all that which was, until then, buried in darkness and concealed from the eyes of mortals. It is certain that Hildegard was acquainted with many things of which the doctors of the Middle Ages were ignorant, and which the investigators of our own age, after rediscovering them, have announced as something entirely new."[190]

The life and works of St. Hildegard throw a flood of light on many subjects that have long been veiled in mystery. It explains why the convents of the later Middle Ages were so famed as curative centers and why the sick flocked to them for relief from far and near. It reveals the real agencies employed in effecting the extraordinary cures that were reported in so many religious houses—cures so extraordinary that they were usually regarded by the multitude as miraculous—and discloses the secret of the success of so many nuns in the alleviation of physical and mental sufferings. It was not because they were thaumaturges, but because they were good nurses, and because of their thorough knowledge of the healing art, that they were able to diagnose and prescribe for diseases of all kinds with a success which, in the estimation of the multitude, savored of the supernatural.

There was also another reason for the fame of convents as sanctuaries of health. They were usually situated in healthy locations where there was an abundance of pure water, fresh air and cheerful sunshine. Then there were likewise a wholesome diet, good sanitary conditions, and, above all, regularity of life.

The same can be said of the hospitals connected with the convents. They were not like some of the public hospitals of the eighteenth and nineteenth centuries in many of the large cities of Europe—repulsive, prison-like structures, with narrow windows and devoid of light and air and the most necessary hygienic appliances—institutions that were hospitals in name, but which were in reality too frequently breeding places of disease and death.[191]

Unlike these, the hospitals presided over by nuns of the type of Hildegard were splendid roomy structures with large windows and abundance of light, pure air, with special provisions for the privacy of the patients, and with sanitary arrangements that not only precluded the dissemination of disease but which contributed materially to those marvelous cures which the good people of the time attributed to supernatural agencies rather than to the medical knowledge and skill of the devoted nuns,[192] who were the real conquerors of disease and death.

But the inmates of the cloister were not the only women who, during the Middle Ages, achieved distinction by their writings on medical subjects and by their signal success in the practice of the healing art. In various parts of Europe, but especially in Italy and France, there were at this time among women, outside as well as inside convent walls, many daughters of Æsculapius and sisters of Hygeia who stood in such high repute among their contemporaries that they received the same honors and emoluments as were accorded to their masculine colleagues.

This was particularly the case in Salerno, which was the venerated mother of all Christian medical schools, and which, for nine centuries, was universally regarded as "the unquestioned fountain and archetype of orthodox medicine." Situated on the Gulf of Salerno, and laved by the cerulean waters of the Tyrrhenian sea, the Civitas Hippocratica, as it was called on its medals, rejoiced in a salubrious climate, and was celebrated throughout the world as the "City sacred to Phœbus, the sedulous nurse of Minerva, the fountain of physic, the votary of medicine, the handmaid of Nature, the destroyer of disease and the strong adversary of death."[193] For to this favored city flocked from all quarters the lame and the halt and those afflicted with the tortures of disease and the disabilities of advancing years. The noble and the simple, crowned heads as well as the poorest of the poor, were found there, all of them in quest of life's most precious boon—health and strength.