In the 19th century, sound scientific thinking and new medical technologies led to advances in every area of medicine, particularly the eradication of many of the world's worst diseases. Of fundamental importance was the discovery of a connection between filth and disease, and public acceptance of the theory led to improved sanitation and other public health measures. Independently established by Louis Pasteur and Robert Koch in the 1870s, the germ theory of disease,
which holds that bacteria and other microbes cause and spread infectious diseases,
enabled scientists to isolate the causative agents of diphtheria, tuberculosis,
and other scourges, leading to the development of vaccines. In 1879, Pasteur accidentally
discovered that bacteria could be weakened, which prevents them from causing disease
but still enables them to trigger immunity in infected individuals. Using
weakened anthrax bacteria taken from the blood of diseased animals, Pasteur
developed the first artificially produced vaccine in 1881. Vaccines for rabies (1885),
cholera (1893), plague (1897), and typhoid (1897) soon followed.
Many new drugs were developed at this time, including acetylsalicylate,
a derivative of the active ingredient in willow bark, a remedy used for combating
fever for more than 2,000 years. Now known as "aspirin," it went on the
market in 1899 after development by the German pharmaceutical company Bayer. Other
drugs to appear in the physician's medicine cabinet included digitalis for heart
ailments, amyl nitrate for angina, quinine for malaria, and sedatives such as chloral
hydrate and paraldehyde.
Scientists of the era discovered that all organisms are composed of cells, determined the functions of nerves and certain parts of the brain, showed the role of the liver in carbohydrate metabolism, and carefully described numerous diseases for the first time. In 1819, the French physician Rene Laennec invented the stethoscope, which was used to listen to the lungs and heart, allowing physicians to hear for the first time "the cry of the suffering organs." Until the 1860s, doctors used long thermometers to take a patient's temperature, a process that took almost 20 minutes. In 1866, Thomas Allbutt introduced the short, clinical thermometer, the use of which was advanced by Carl Wunderlich, who showed that fever is a symptom, not a disease. In 1895, Wilhelm Conrad Rontgen made the first "medical" X-ray, named for a then unknown type of radiation, which for the first time enabled doctors to see inside the body without surgery.
Modern surgery emerged in the 19th century as well. Physicians recognized the three major obstacles to successful surgery -- pain, infection, and bleeding. Two American dentists, Horace Wells and William Morton, discovered anesthesia in the 1840s. By reducing the trauma of surgery for patients, anesthesia allowed doctors to take more time over their work and to apply surgery to more ailments.
In 1867, the British surgeon Joseph Lister popularized antiseptic
surgery and sterilized equipment, and the practice dramatically reduced infections
in surgery patients and improved the odds of survival. Around 1890, William Halsted
introduced the practice of wearing sterilized rubber gloves during surgery. By
the end of the 19th century, the age-old practice of bloodletting was finally
abandoned. The modern blood-type classification system, used to replenish a patient's
blood through transfusions, began with the 1900 discovery of the ABO blood groups
by the Austrian scientist Karl Landsteiner.
Not all medical milestones were achieved in laboratories and
operating rooms. In 1889, William Osler was appointed the first physician-in-chief
at John's Hopkins Hospital in Baltimore, where he revolutionized the way the
medical curriculum was taught. Osler insisted that students learn at the
bedside, implementing his belief that "the good physician treats the
disease; the great physician treats the patient who has the disease." Students
took patient histories, conducted physical examinations, and studied laboratory
results, leading to a more interactive and humane treatment of medical conditions.
Osler established the medical residency, in which doctors in training make up much
of a hospital's medical staff. This system remains in place today in most teaching
hospitals.
In the 20th century, advances in medicine came rapidly, changing
the nature of death's threat. When the 20th century began, life expectancy in the
United States was 47 years. In 2000, the average life span had increased to almost
77 years. The dramatic decline in the mortality rate is in large part due to
the advancement of medicine, as well as the development of drugs to combat infectious
diseases.
In 1901, Walter Reed, a U.S. Navy pathologist, discovered
that viruses could cause disease in humans. His experiments proved that yellow fever
was caused by a virus transmitted by mosquitoes. Development of electron microscopes
in the 1930s gave scientists their first glimpse of viruses, and tissue culture
techniques enabled researchers to grow viruses in the laboratory for drug
testing, preparation of vaccines, and other purposes.
Another type of disease-causing agent, distinct from viruses,
was first isolated in 1982. Called prions, these particles consist of a single protein;
they can be transformed into abnormal shapes capable of destroying cells. Prions
cause spongiform encephalopathies, fatal diseases characterized by the breakdown
of brain tissue -- the most famous of which is commonly known as mad cow
disease.
Hormones were isolated in 1901, and the therapeutic use of hormones
began 20 years later when insulin, a hormone produced by certain pancreatic cells,
was injected into a person with diabetes, a disease that slows or stops the
body's natural production of insulin.
Perhaps the most significant contribution in the field of
endocrinology came 50 years later, with the creation of the birth control pill.
In the early 1950s, Gregory Pincus, an American biologist and researcher, discovered
that injections of the hormone progesterone would inhibit ovulation and prevent
pregnancy. Seed money for this effort was provided by Margaret Sanger, a lifelong
advocate for women's rights. At the same time, Carl Djerassi created an orally
effective form of synthetic progesterone. It was another decade before
"the pill" received F.D.A. approval and became commercially available,
ushering in both a medical and social revolution.
In the first decade of the 20th century, scientists realized
that certain "accessory food factors" are essential to good health. In
1911, Casimir Funk (1884-1967) found the first of these factors, B, and in a 1912
paper proposed the factors be called vitamins. Soon after the discovery of
vitamins A (1913), D (1922), E (1922), C (1928), and K (1934), these substances
soon became widely available.
Paul Ehrlich (1854-1915), a German scientist, helped found modem
chemotherapy -- the use of chemicals to fight disease -- a treatment that proved
effective against diseases that did not respond to serum therapy. He began to
work with substances that killed or inhibited the growth of parasites, and in
1910 he successfully synthesized Salvarsan, the "magic bullet" used to
cure syphilis.
Medicine was revolutionized in 1928, when Alexander Fleming discovered
the antibiotic properties of penicillin, but he was unable to produce it in a form
pure enough to use on patients. Ten years later, Howard Florey and others at
Oxford University solved this problem, and by World War II techniques were
developed in the United States for the commercial production of the drug. Its disease-fighting
potential was recognized in the early years of World War II, and it saved the lives
of countless wounded soldiers. Today a number of penicillins are available, and
they are among the most widely used antibiotics.
In 1900, pneumonia and tuberculosis were the leading causes of
death in the United States, but by 2000 these and most other common bacterial
infections had been brought under control, although scientists now recognize that
microorganisms have the ability to develop a resistance to these medications.
Genetics, as a distinct field of study, came to prominence in
1900, when three botanists independently rediscovered the basic laws of heredity
published by Gregor Mendel in 1866. By 1911, Thomas Hunt Morgan (1866-1945) had
discovered that mutations could occur in genes, and by the 1940s scientists had
established that all organisms as well as viruses can mutate.
In the early 20th century, surgeons began to specialize and new
fields emerged, building on the efforts of a few extraordinary individuals. Not
for the first time, the theater of war made an enormous contribution to the progress
of medicine. Harold Gillies, a New Zealand-born, British Red Cross doctor in World
War I, saw that while soldiers could survive their battle wounds, surgeons had
neither the skill nor the time to deal with their often dramatic disfigurements.
Gillies devoted himself to the study and practice of plastic surgery, founding
Queen's Hospital in Kent, England, where more than 10,000 reconstructive surgeries
were performed. The techniques he invented, including skin grafts, were adopted
by surgeons around the world and ushered in the era of reconstructive and, ultimately,
cosmetic surgery.
Working in some of America's finest hospitals, including John's
Hopkins Hospital in Baltimore and Peter Bent Brigham Hospital in Boston, Harvey
Cushing emerged as the first true neurosurgeon in the early 20th century. Among
his many innovations, Cushing created a way to stem the flow of blood with clamps
and cuffs, minimizing the possibility that the patient would bleed to death. He
pioneered the use of the "electric scalpel" and demanded that his team
work with masks and gloves to minimize infection. His patients were the first
to receive around-the-clock nursing care after surgery, and this type of
postoperative treatment was the forerunner of intensive care units. Taken
together, Cushing's contributions made brain surgery safer and more effective.
Other surgical milestones during this period included the first
successful appendectomies, performed in Davenport, Iowa, in 1885 by Dr. William
West Grant, and at roughly the same time by Dr. H. Hancock in England. In 1932,
the American surgeon Michael E. DeBakey developed a roller pump that became an essential
component of the heart-lung machine, which enabled the first open-heart surgery,
performed by John H. Gibbon, Jr. in 1953. In 1966, DeBakey implanted the first mechanical
heart in a human, and the successful transplantation of the liver (1963), lung (1963),
pancreas (1966), intestine (1966) soon followed. In 1967, Dr. Christiaan Barnard
performed the first successful human heart transplant. Bone marrow transplants began
in 1964, and today stem cell transplants represent one of the most exciting-and
controversial-frontiers in modern surgery. In 1990, the so-called laparoscopic technique
was perfected, allowing surgeons to make much smaller incisions in the patient's
abdomen to remove small organs through the navel.
Twentieth-century technologies such as computers, electronics,
fiber optics, lasers, and ultrasound were all incorporated into medicine, making
diagnosis more accurate and treatments safer. Mammography for diagnosing breast
cancer was introduced in 1913 and the electroencephalograph (EEG) for recording
brain waves in 1929. The heart can be monitored by recording electrical activity
via skin electrodes with an electrocardiography (EKG) machine; magnetic resonance
imaging (MRI) greatly improved the imaging provided by X-rays. A CAT scan combines
X-ray equipment with computers that create detailed images of body tissue, allowing
for greater ease in tough diagnoses.
Great advances also occurred in the construction of artificial
body parts: aluminum, titanium, plastic resins, and three-dimensional computer
modeling are used to build sophisticated limbs and joints.
Through the past millennia, the human life span has increased
as people have learned how to prevent and treat illness, although in spite of medical
advances, humans continue to face major health challenges. While many infectious
diseases have been brought under control, AIDS, Lyme disease, and other emerging
diseases discovered only in recent decades have created new medical battlefields.
As people live longer, there is a growing incidence of arthritis, Alzheimer's disease,
and heart failure. However, a better understanding of human biology, genetics, and
psychology has led to improved preventive measures, diagnostic tools, and therapies.
(‘The New York Times ‘Smarter by Sunday – 52 Weekends of Essential Knowledge
for the Curious Mind’)
