The Victorian Era

How Did Germ Theory Change Medicine

Article · Science & Invention · The Victorian Era, 1837–1901

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Germ theory, the doctrine that infectious diseases are caused by micro-organisms rather than by miasmas, by the imbalance of the humours, or by divine judgement, was the central medical revolution of the Victorian era. It was established in stages between 1835 and 1884, applied to surgery by Joseph Lister in 1865, and consolidated in the 1880s and 1890s by the identification of the bacterial causes of tuberculosis, cholera, typhoid, diphtheria, and a dozen other diseases. The new theory transformed the practice of surgery, the design of hospitals, the treatment of epidemics, and the public health of the British nation. The history of the theory is part of the wider history of Victorian Medicine and Public Health, and it is connected to the How did Florence Nightingale change nursing? reform and to the What was the Great Stink of London? sanitary crisis.

From Miasma to Microbe

The older miasma theory held that epidemic diseases were caused by the bad air that rose from rotting matter, from swamps, from sewers, and from the overcrowded slums of the industrial city. The miasma theory had the practical advantage of pointing in the right direction: bad smells often did correlate with disease, and the sanitary reforms undertaken in its name, the new sewers, the new water supplies, the slum clearance, were often effective in reducing the incidence of disease. The great sanitary reformers of the mid-Victorian period, Edwin Chadwick, Thomas Southwood Smith, and John Simon, were largely miasmatists, and the new How was the London sewer system built? was in part a response to the miasma theory.

The miasma theory could not, however, explain why one patient in a hospital ward would die of cholera while the patient in the next bed would survive, why a clean house could be the site of a fatal epidemic, or why some diseases were contagious while others were not. The new evidence came from a sequence of investigations between 1835 and 1884.

The Discovery of Micro-organisms

The discovery of the microbial world had begun in the seventeenth century, when Antonie van Leeuwenhoek, a draper and amateur lens-grinder in Delft, communicated to the Royal Society of London his observations of “animalcules” in rainwater, in well water, in pepper water, and in scrapings from the human mouth, between 1674 and 1683. Leeuwenhoek’s single-lens microscopes, the most powerful of the period, magnified up to 275 times, and his drawings of bacteria, protozoa, spermatozoa, and red blood cells were not improved upon for nearly a century. The instruments that would allow the systematic study of these organisms, the achromatic compound microscope, were developed in the 1820s and 1830s by the opticians Joseph Jackson Lister (father of the surgeon) and Andrew Ross, and the cell theory of Matthias Schleiden and Theodor Schwann of 1838-39 gave the new observations a theoretical framework.

Bassi, Semmelweis, and the First Evidence

The first serious evidence that a specific micro-organism caused a specific disease came from the Italian naturalist Agostino Bassi, who in 1835 showed that the muscardine disease of silkworms was caused by a fungus, later named Beauveria bassiana in his honour. Bassi’s work was taken up by the microscopists of the 1840s, and the principle of contagion by a living organism was widely discussed. The Hungarian physician Ignaz Semmelweis, working in the first clinic of the Vienna General Hospital, showed in 1847 that the incidence of childbed fever in the ward served by medical students was three times that in the ward served by midwives, and he attributed the difference to the cadaveric material that the students carried on their hands from the autopsy room to the lying-in ward. The introduction of hand-washing with chlorinated lime in May 1847 reduced the mortality of the first clinic from 18 per cent to under 3 per cent within a year, and Semmelweis’s The Etiology, Concept, and Prophylaxis of Childbed Fever of 1861, ignored in his lifetime, became a founding text of the new theory. The English physician Thomas Watson published his Lectures on the Principles and Practice of Physic in the 1840s, and the work of John Snow on cholera, of William Budd on typhoid, and of John Simon on the sanitary movement provided the parallel British evidence.

Pasteur and the Germ Theory

The decisive work was done in Paris by Louis Pasteur, a chemist by training who had made his reputation in the 1840s and 1850s by the study of the optical activity of tartrate crystals. From 1857 onwards Pasteur turned to the study of fermentation, and he showed that the fermentation of wine, beer, vinegar, and milk was caused by specific micro-organisms, the yeasts and the bacteria, and not by spontaneous generation. The work of Pasteur refuted the long-standing theory of spontaneous generation in a series of famous experiments with swan-necked flasks between 1860 and 1864, and it laid the foundation of the new science of microbiology.

Pasteur turned next to the diseases of animals and humans. He showed that the pébrine disease of silkworms, which had ruined the French silk industry, was caused by a micro-organism, and he worked with Charles Chamberland and Émile Roux on the diseases of chickens (chicken cholera), of cattle (anthrax), and of pigs (swine erysipelas). The famous public experiment at Pouilly-le-Fort in May-June 1881, in which twenty-four sheep, six cows, and a number of goats were vaccinated with Pasteur’s attenuated anthrax vaccine and then exposed to a lethal dose, was a public demonstration of the practical application of germ theory that was reported across the world. Pasteur’s rabies vaccine, developed in his Paris laboratory at the rue d’Ulm and first used on the nine-year-old Joseph Meister on 6 July 1885, was the first effective vaccine against a human disease since Jenner’s cowpox vaccine of 1796, and the Institut Pasteur, founded by public subscription in 1887, was the model for the great research institutes of the twentieth century.

Koch and the New Bacteriology

The German physician Robert Koch, working in a small laboratory in Wollstein in the Prussian province of Posen, established the techniques by which the new theory could be confirmed. Koch had shown in 1876 that anthrax was caused by a specific bacillus, Bacillus anthracis, and he had used the new aniline dyes, introduced by Paul Ehrlich and Carl Weigert, to stain the bacteria and the new Abbe condenser of Carl Zeiss to make them visible under the microscope. Koch’s postulates, four criteria for establishing a causal link between a particular micro-organism and a particular disease, were published in the second of his papers on tuberculosis in 1884: the organism must be found in all cases of the disease, it must be isolated from the host and grown in pure culture, it must reproduce the disease when introduced into a healthy host, and it must be recovered from the inoculated host.

Koch applied the postulates in his own laboratory and in the Imperial Health Office in Berlin, where he was appointed in 1880. He identified the bacillus of tuberculosis (Mycobacterium tuberculosis) in 1882, the bacillus of cholera (Vibrio cholerae) in 1883-84, and his pupils and rivals, working in the new bacteriological institutes that sprang up across Europe, identified the bacilli of typhoid (1884), of diphtheria (1884, by Edwin Klebs and Friedrich Loeffler), of tetanus (1884, by Arthur Nicolaier), of plague (1894, by Alexandre Yersin and Kitasato Shibasaburo), and of many other diseases. Koch’s tuberculin, prepared from cultures of the tuberculosis bacillus and announced in 1890 as a “remedy” for the disease, was not the cure he had hoped, and his controversial claim, at the International Medical Congress of 1901, that bovine and human tuberculosis were different diseases was a serious misjudgement, the Royal Commission on Tuberculosis of 1898-1901 having shown the opposite.

Lister and the Antiseptic Surgery

The first practical application of the new theory to medicine was the antiseptic surgery introduced by Joseph Lister at the Glasgow Royal Infirmary in 1865. Lister, who had read Pasteur’s work on fermentation, reasoned that if micro-organisms caused fermentation, they might also cause the putrefaction of wounds. He began to use carbolic acid, the creosote extracted from coal tar, to sterilise wounds, surgical instruments, the hands of the surgeon, and the air of the operating theatre, and he published his results in a series of papers in The Lancet in 1867. The antiseptic method cut the mortality of compound fractures at the Glasgow Royal Infirmary from over 40 per cent to under 15 per cent within a decade, and the principle of antiseptic practice was rapidly adopted in the German-speaking world and slowly in the British hospitals, where the old surgical establishment was sceptical of the new “germ theory” until the 1880s.

The later development of aseptic surgery, in which the surgeon, the instruments, the dressings, and the operating theatre were all kept free of germs by the use of steam sterilisation, sterile gowns, gloves, and instruments, was a direct extension of Lister’s work. The new operating theatres of the 1890s, with their tiled walls, glass operating tables, and steam-sterilised instruments, were the architectural expression of the new germ theory. The story of the antiseptic surgery is part of the wider history of Victorian Medicine and Public Health, and the new hospital buildings of the period were designed with the new germ theory in mind.

The New Pharmacology and the Magic Bullet

The germ theory of disease also led to the development of new vaccines, antitoxins, and the science of chemotherapy. The British bacteriologist Almroth Wright, working at the Army Medical School at Netley and then at St Mary’s Hospital in London, developed a vaccine for typhoid in 1896, and the British army was the first in the world to be routinely vaccinated against typhoid, with a campaign in the Indian and African campaigns of 1896-1900. The diphtheria antitoxin, developed by Emil von Behring and Kitasato Shibasaburo in 1890 and first used on a large scale in 1894, was the first effective treatment for a specific bacterial disease, and the work of Behring earned him the first Nobel Prize in Medicine in 1901. The German chemist Paul Ehrlich, working at the Institute for Experimental Therapy in Frankfurt from 1899, developed the idea of the Zauberkugel, the magic bullet, a chemical that would specifically target a disease organism without harming the patient. Ehrlich’s Salvarsan, an arsenic-based compound that was effective against syphilis, was developed in 1909 and was the first of the chemotherapeutic agents that would eventually lead to the sulphonamides and the antibiotics of the twentieth century.

Public Health and the New Theory

The acceptance of germ theory also transformed the public health legislation of the 1870s and 1880s. The Public Health Act of 1875, the consolidating act of 309 sections, gave local authorities the powers that they had long demanded, and the Rivers Pollution Prevention Act of 1876 made it an offence to discharge sewage into a river. The Sale of Food and Drugs Act of 1875 created a system of public analysts and inspectors that was the foundation of the modern food safety system. The Infectious Disease Notification Act of 1889 made the notification of certain infectious diseases compulsory, and the Public Health (London) Act of 1891 created the London County Council as the sanitary authority for the capital. The vaccination acts of 1891 and 1898, which removed the fees for vaccination and introduced a conscientious objection clause, were the last major Victorian enactments in this field, and the Royal Commission on Tuberculosis of 1898 was set up in response to Koch’s claim that bovine and human TB were different diseases.