Mycobacterium tuberculosis and the Cause of Consumption

Experts seem to agree that the scourge of tuberculosis, which had been steadily worsening for at least 200 years, climaxed in western Europe around the end of the eighteenth century or the beginning of the nineteenth—in either case while the industrial revolution was in full swing. In the year 1800, according to one model, the mortality rate from tuberculosis peaked at 1,000/ 100,000 inhabitants (1) and accounted for one of every four deaths recorded in parish registries from England. Similar rates from records kept in New England at the same time attest to the colossal burden of the disease in the United States as well (2). Burgeoning industrialization created the need for a greatly enlarged workforce in manufacturing cities. Hoards of people converged from rural areas, mainly young adults, but including also adolescents and children. Living and working conditions were appalling and consisted, for many people, of overcrowded dwellings and congested factories where sanitation and hygiene were abominable. Malnutrition was epidemic and medical care, if it can be dignified as such, was virtually useless in those rare instances when it was available. No wonder tuberculosis prospered. During the eighteenth and nineteenth centuries, consumption was considered incurable by most people, patients and physicians alike. Not surprisingly, speculation abounded concerning the cause of what was by far the number one killer of family, friends, and neighbors. Different theories were passionately espoused by leading medical authorities of the day. Some experts advocated contagion, others a constitutional hereditary defect, atmospheric imbalances, the depredations of stress, or an inevitable consequence of the degeneration of the human race; even the role of divine retribution was occasionally evoked. The controversy flourished despite the report in 1865 by Jean-Antoine Villemin, a French military surgeon, that he had been able to transmit tuberculosis from humans to rabbits by inoculation, the first clear demonstration of contagion (3); Villemin’s observations were confirmed by Edwin Klebs, Julius Cohnheim, and Carl Salomonsen in elegant experiments, but the causative agent remained elusive and skeptics prevailed (for review and references see Reference 4). Not long after, the debate was concluded— once and for all—by one of the most definitive pronouncements in medical history, though by no means all physicians believed it, and there are two accounts of the events surrounding the declaration.