Many other important discoveries were made by Harvey, particularly in embryology. He demonstrated that the embryo chicken is formed by gradual development and processes of differentiation and not, as had previously been believed, from a minute perfect chicken.
Microbes were discovered in 1683 by Antonius von Leeuwenhoek (1632-1723), when he was examining some scrapings from his teeth. He saw for the first time the long and short rods of bacilli and bacteria, the spirillum and the micrococci. He tried means for destroying them and met with a fair degree of success with a gargle composed of a mixture of vinegar and hot coffee. This experiment was one of the early anticipations of antiseptic surgery, which was invented by Lister in the nineteenth century.
A French surgeon, Ambroise Paré (1517-1590) was a pioneer in the treatment of wounds. The old method was to use boiling oil. He found that by simply cleaning and bandaging wounds he could get better and quicker results than with hot oil, which was a very painful treatment. Paré used ligaments in stopping hemorrhages, improved the surgery in harelip and hernia operations and for suprapubic lithotomy. He learned the principles of these operations from Peter Franco (1505-1570), an itinerant surgeon, who had much skill in operations for kidney and bladder troubles.
Franz de la Boë (1614-1672), a professor in the university of Leyden, who is best known under the name of Sylvius, the discoverer of the brain fissure of Sylvius, founded a new school of chemical medicine. Van Helmont suggested to him the possibility of the stomach being the seat of many common disorders. When this was investigated, many experiments were made with new medicines. The success of these experiments led to a great reform in medical practice. Thomas Willis (1622-1675), an English physician, completed the development of the treatments suggested by Van Helmont and Sylvius as a result of their studies of the works of Harvey.
Another great English medical genius arose to establish the practice of medicine on a scientific basis. Thomas Sydenham (1624-1689) founded a school of medicine in accordance with these three principles: (1) Accurate descriptions of the courses of diseases, (2) following a fixed method of treatment in each disease, (3) searching for specific remedies for each diseased condition.
The results of these teachings were very pronounced. Before Sydenham's time, the only drug used in medicine was an extract of cinchona. The Dutchmen above named and Sydenham discovered many active medicinal substances. Sydenham's principal discovery in materia medica was that of the properties of laudanum.
William Gilbert, court physician to Queen Elizabeth of England, while Galileo and Stevin were developing the laws of gravitation and hydrodynamics, undertook the investigation of the laws of terrestrial magnetism and chemistry. His researches in chemistry were extensive and valuable. His fame, however, was perpetuated by his study of magnetism and electricity. He found that the earth is a vast magnet with north and south poles. His remarkable textbook on magnetism covered many of the fundamental facts known to-day. He noted the distinction between magnetism and electricity, described electrical charges, the principles of conductivity and methods for magnetizing iron. Galileo wrote of him: "I extremely admire and envy this author."
The mercurial barometer and its laws were discovered by Evangelista Torricelli (1608-1647) a student of Galileo. By means of his barometer, Torricelli was able to make great advances in knowledge relating to the physics of the air and to gas pressures, and he investigated the principles of hydraulics. The microscope, telescope, sextant and other instruments were greatly improved by him, and his mathematical work ranks only second to his contributions to experimental science.
The Torricellian tube, used as a barometer, was a means of creating a vacuum, which was formed at the top of the column of mercury. Pascal, the French mathematician, took up the study of the physics of the vacuum and published an important work on his own experiments. These and other experiments made by European scientists prepared the ground for, and suggested, the investigations of gases and vacua by Boyle, Mariotte, and others which finally resulted in the invention of the steam engine and many other modern machines.