In his A Treatise on the Consumption of the Lungs (1722), Edward Barry describes the influence of environmental stimuli upon an inherited malady such as consumption: “This constitution to some is natural and hereditary; but in many others be acquired, by the intemperate use of a hot, aromatic, saline, or animal Diet, or by previous Disorders, which relax the vessels, and deprive the Blood of the oily and balsamic parts, and render its salts too active and volatile.” Like many other physicians of his time, Barry acknowledged “that phthisis, which is hereditary, and proceeds from a Constitution inclined to that Distemper, is most commonly fatal.” Georgian medicine advocated a patient history that began before birth, centering on an individual whose physical and moral health was dependent upon hereditary qualities. The relationship between the parent’s constitution and their offspring was an obvious empirical fact, though any constitutional defects—including hereditary dispositions to disease (diathesis)—were believed to be inherited along with phenotypical characters. “Still a period when both learned physicians and the common man saw disease as the sum of one’s transactions with the environment,” physicians favoured explanations supporting hereditary disposition, particularly for chronic diseases with complex etiology as phthisis, scrofula, or gout. While the etiology of other diseases could also be attributed to heredity, historian Elizabeth Lomax points out that hereditary disposition played a larger part in the etiology of consumption, while a disease like scrofula seemed “to be precipitated by conditions associated with poverty,…tuberculosis attacked the rich and poor alike, leaving heredity as a prime suspect in causality.” So familiar was the hereditary transmission of maladies that not until the 1840s were the first systematic attempts made to evaluate the hereditarian thesis in Britain.
However, in the opinion of most Georgian physicians, most maladies identified as heritable were without remedy. Recognizing the importance of reassuring the patient, Benjamin Marten wrote, “no greater Harm can be well done to Consumptive Persons, than for People to tell them they are incurable.” It is plausible that the concept of hereditary predisposition was constructed as an approach against the hopelessness of incurability. Historian J.C. Waller states that “instead of building a theory of hereditary disease on the basis of raw statistical data, doctors had constructed a concept—predisposition—for which there as scant evidence, and then used it to make it appear that the failure of children to inherit their parent’s maladies was exactly what a rational theory of heredity would predict.” Emphasizing on this point, Waller asserts that the concept of hereditary disease arose as a by-product of a link between the notion of incurable disease and the ancient concept of unchanging individual constitution. He further explicates that “this conceptual structure was formed because of a desire on the part of the medical profession to rationalize, and to some extent to excuse, its inability to treat a range of persistent maladies.” In other words, the inherited malady is a spin-off of construction of the category of constitutional malady familiar in the Hippocratic-Galenic theory of medicine. For Waller, despite the fact that from the late eighteenth century, “the concept of hereditary disease diathesis was virtually ubiquitous in discussions of the origins of chronic illness,” this does not explain why “the concept of heredity was so routinely applied to the sorts of medical conditions that most of the profession utterly despaired of curing.” Physicians generally recognized a conceptual association between heredity and incurability and if Waller is correct in his objection, why did these physicians readily accept hereditary illness and devise cures though they faced evidential and theoretical difficulties with the concept?
Part of the answer is obvious. As historian Charles Rosenberg explains, “for the physician to have thrown up his hands, to have confessed ignorance and impotence would have been a real failure of commitment.” Nevertheless, for the rational physician who could not single out the determinant factor for an inherited phthisis, would it not have been beneficial to simple remove the hereditary taint out of his diagnosis? Why was a hereditary explanation so necessary? I believe in part, the hereditary theory of phthisis was a theory of convenience. Not only could the hereditary theory explain away any ignorance the physician had about disease patterns as Waller argues, but it could also account for patterns of moral and social fallings in society, particularly as the concept of hereditary predisposition encouraged patients to overcome their diathestic limitations by implementing personal responsibility through individual lifestyle. In short, hereditary predisposition served its purpose as an ideology, for it “served effectively in helping dramatize the need for temperance for moderation in diet and sexual relations.”
A hereditary predisposition of phthisis made sense of an otherwise inexplicable distribution of disease. It explained why a husband and wife slept together on the same bed and only one succumbed to the wasting malady. It also provided an acceptable rationale for treatment management in a time when infection was highly regarded as untreatable. As a socially constructed disease, consumption was also a fundamentally destructive social force, with factors such as professional interests, ideologies, and socio-political pressures all playing a role. Rosenberg has argued that while the formal context of scientific knowledge of heredity remained largely unchanged between 1800 and 1900, the social applications of heredity has shifted markedly in scope and emphasis. “It is an intellectual evolution,” Rosenberg writes, “which illustrates with remarkable clarity the way in which ideas putatively scientific can be shaped by the need of society to rationalize, to understand, to find plausible sanctions for social action.” Social attitudes become relevant when they are sanctioned by the scientific doctrines advocating them.
 Barry, A Treatise on the Consumption of the Lungs, 222, author’s emphasis.
 Barry, A Treatise on the Consumption of the Lungs, 245. A constitution is generally defined as a “view of the body as an organized structure, acting as a whole, its constituent traits being inherited en bloc” (R.C. Olby, “Constitutional and Hereditary Disorders.” In Companion Encyclopedia of the History of Medicine volume 1. Eds. W.F. Bynum and Roy Porter (London & New York: Routledge, 1993), 413.
 Sean Quinlan also points out that this perception may have been at odds with the Enlightenment ideal of tabula rasa, where an individual was born a sensible being and conditioned by his experiences with the environment. The fixed hereditary state of an individual was part of a conceptual shift within French medicine, where physicians began to develop new approaches and meanings to reproduction, sexual generation, and thus, inheritance. See Quinlan’s paper, “Inheriting Vice, Acquiring Virtue: Hereditary Disease and Moral Hygiene in Eighteenth-Century France.” Bulletin of the History of Medicine 80 (2006).
 Rosenberg, “The Bitter Fruit,” 157.
 Lomax, “Hereditary or Acquired Disease?” 373.
 J.C. Waller, “The Illusion of Explanation: The Concept of Hereditary Disease, 1770-1870.”Journal of the History of Medicine 57 (2002), 415
 Marten, A New Theory of Consumption, 3.
 Waller, “The Illusion of Explanation,” 421.
 Waller, “The Illusion of Explanation,” 413.
 Waller, “The Illusion of Explanation,” 414.
 Waller, “The Illusion of Explanation,” 410.
 Waller, “The Illusion of Explanation,” 426.
 Rosenberg, “The Bitter Fruit,” 161.
 Rosenberg, “The Bitter Fruit,” 161.
 F.B. Smith, The Retreat of Tuberculosis, 1850-1950 (London: Croom-Helm, Ltd., 1988), 40.
 Rosenberg, “The Bitter Fruit,” 154-5.
 Rosenberg, “The Bitter Fruit,” 155.