Overview: Life Sciences and Medicine 1700-1799
Overview: Life Sciences and Medicine 1700-1799
Though his research did not directly involve the life sciences, the seventeenth-century physicist Isaac Newton (1642-1727) greatly influenced how living things were studied in the eighteenth century because of his emphasis on finding simple laws underlying the complexities of movement. The earlier work of philosopher Francis Bacon (1561-1626) was also influential in the eighteenth century. Bacon stressed the importance of direct observation and of experimentation as keys to progress in science. In addition, the explorations around the globe in the sixteenth and seventeenth centuries, as well as the development of the microscope in the seventeenth century, opened up new worlds filled with fascinating life to be studied.
As explorers sent back a treasure trove of new species to Europe, the problem of how to classify or organize them became urgent. While the British botanist John Ray (1628-1705) and others developed various classification schemes, it was the system of Swedish botanist Carolus Linnaeus (1707-1778) that became most widely accepted. He based his classification of plants on the structure of their flowers and gave each species two names, the first for the genus, or general category to which the organism belonged, and the second for the species itself. French zoologist Georges Buffon (1707-1788) published a multi-volume survey of the animal world, while other zoologists focused on particular groups of organisms, with René de Réaumur (1683-1757) publishing a massive work on insects.
One of the driving forces of seventeenth-century life science, particularly in Britain, had been natural theology, the attempt to learn about God by studying design in nature. There were, however, others who argued that there was no need to invoke divine intervention to explain life processes. Following the lead of the seventeenth-century French philosopher René Descartes (1596-1650), they developed a mechanistic concept of life, seeing it as governed by the same physical principles that Newton had identified as underlying movement in the nonliving world. Their ideas were opposed by vitalists, who saw life processes as involving principles unique to life and different from those in the nonliving world. These questions continued to be debated throughout the eighteenth century.
Another controversy in eighteenth-century life science involved development—how the form of an individual emerged. Some scholars, called preformationists, argued that in the case of human development, for example, the germ from which an individual arose contained a tiny replica of the human body, and all that happened during gestation was that this preformed figure increased in size. Others, who adopted epigenesis, contended that the human form was not preexisting, but instead only gradually developed and increased in complexity during that development.
Another debate at this time involved the question of spontaneous generation, of whether living organisms, particularly microscopic organisms, could arise from nonliving matter or whether they could only come from others of their kind. In 1767 Lazzaro Spallanzani (1729-1799) challenged the theory of spontaneous generation by demonstrating that microbes will not appear in flasks of broth that have been boiled and sealed. This controversy, however, would continue far into the nineteenth century.
Anatomy and Physiology
Francis Bacon's call for careful observation and experimentation influenced the development of anatomy and physiology. Marie-François Bichat (1771-1802) discovered that the body's organs are made up of many different kinds of tissues; his work opened the way for later studies on the cellular organization of tissues. There were also many efforts to discover the relationship between anatomy and disease, with Giovanni Morgagni (1682-1771) being particularly important in the growth of pathology, the study of abnormal anatomy.
Physiology, the study of function, also blossomed. In plant physiology, careful experimentation was done in a number of areas: Stephen Hales (1677-1761) studied the movement of water through plant tissues; Jan Ingenhousz (1730-1799) established that sunlight was necessary for the production of oxygen in leaves and thus for photosynthesis; Joseph Kölreuter (1733-1806) described how insects and birds carry pollen from one plant to another.
In animal physiology, digestion and movement were given particular attention and there was a great deal of study of the nervous system. Hales also made important contributions to this field with his discovery of the connection between the spinal cord and reflex movements in frogs. Albrecht von Haller (1708-1777) was the first to demonstrate that nerves stimulate muscle contraction, and Luigi Galvani (1737-1798) discovered the electrical basis of nerve impulses. The field of psychology, a term coined by David Hartley (1705-1757), began at this time and dealt with the study of the mind and behavior. A number of philosophers, including David Hume (1711-1776) and François Voltaire (1694-1778), originated theories of the mind and of the human sense of morality.
Medicine: Prevention of Disease
The eighteenth century saw a number of discoveries important to the prevention of disease, though in several cases the full impact of these discoveries was not felt for some time. For example, Percival Pott (1714-1788) found a high incidence of cancers of the scrotum and nasal cavity among chimney sweeps. This provided the first link between environmental factors and cancer, links that are still being investigated. James Lind (1716-1794) demonstrated experimentally that citrus fruits could prevent and cure scurvy, a nutritional deficiency common on long sea voyages and ultimately linked to a lack of vitamin C. At the end of the century, Edward Jenner (1749-1823) developed the first vaccine, an inoculation to prevent against the dreaded disease of smallpox. The vaccine contained cowpox, a virus that was less dangerous than the one causing smallpox, yet one that produced an immune response providing protection against the more serious infection.
It was also in the eighteenth century that the field of public health originated with the aim of improving living conditions, thus controlling and preventing disease. Johann Peter Frank (1745-1821) wrote a six-volume work on medical policy and identified poverty as the "mother of disease." John Howard (1726-1790) campaigned for improved cleanliness in poorhouses, prisons, and hospitals, where sanitary conditions had been abominable. In general, there was a growth in the number and importance of hospitals, with a wave of construction occurring in Europe after 1730 and in America after 1750.
Medicine: Treatment Methods
There were changes in a number of branches of medicine during the eighteenth century. Franz Mesmer (1734-1815) developed a controversial technique of hypnotism to cure disease. Also, surgery became a more common and respected field as surgeons developed techniques for treating such conditions as ear infections and cataracts and for the removal of cancerous lymph glands. The British surgeon John Hunter (1728-1793) was a key figure in the transformation of surgery from a craft into an experimental science through his research on inflammation.
Along with the increased status of surgeons, there was a move in obstetrics from female to male domination of the field of midwifery, where new instruments such as the forceps were used in delivering babies. In dentistry, Pierre Fauchard (1678)-1761) made advances in techniques for filling cavities and Philipp Pfaff popularized casting methods for making false teeth.
By the close of the eighteenth century the life sciences were poised for the great advances that would occur in the next century. Jean Baptiste de Lamarck (1744-1829), building on the work of his teacher Buffon, would soon publish his theory of evolution, asserting that species change over time. Later, Charles Darwin (1809-1882) would offer an even more convincing evolutionary theory. Experimentation would continue to become more important in the study of organisms, with Claude Bernard (1813-1878) popularizing the experimental method in biology and doing significant research in physiology. Work toward improving sanitation would expand with the building of sewer systems and by providing cleaner water supplies in cities. Medicine would also see the development of antiseptic procedures in surgery and the establishment of the germ theory of infectious disease.