"Among all the saintly religious who have practised medicine or written about it in the Middle Ages, the most important is without any doubt St. Hildegarde...." With regard to her book he says: "All those who wish to write the history of the medical and natural sciences must read this work, in which this religious woman, evidently well grounded in all that was known at that time in the secrets of nature, discusses and examines carefully all the knowledge of the time." He adds: "It is certain that St. Hildegarde knew many things that were unknown to the physicians of her time." Some of Hildegarde's expressions are startling enough because they indicate discussion of, and attempts to elucidate, problems which many people of the modern time are likely to think occurred only to the last few generations. For instance, in talking about the stars and describing their course through the firmament, she makes use of a comparison that seems strangely ahead of her time. She says: "Just as the blood moves in the veins, causing them to vibrate and pulsate, so the stars move in the firmament, and send out sparks as it were of light, like the vibrations of the veins." This is, of course, not an anticipation of the discovery of the circulation of the blood, but it shows how close were men's ideas to some such thought five centuries before Harvey's discovery. For Hildegarde the brain was the regulator of all the vital qualities, the centre of life. She connects the nerves in their passage from the brain and the spinal cord through the body with manifestations of life. She has a series of chapters with regard to psychology, normal and morbid. She talks about frenzy, insanity, despair, dread, obsession, anger, idiocy, and innocency. She says very strongly in one place that "when headache and migraine and vertigo attack a patient simultaneously, they render a man foolish and upset his reason. This makes many people think that he is possessed of a demon, but that is not true." These are the exact words of the saint as quoted in Mlle. Lipinska's thesis.