In this dissertation, the occurence of tuberculosis and it's causes are studied with special attention to developments in Sweden. The perspective is a comparative one. Secular trends as well as shortterm fluctuations are analysed. The decrease in the mortality rate in the West that has taken place in recent centuries has primarily been the result of a decrease in infectious diseases. Among the factors which have been cited as having an decisive role are: the decline in the death rate, the role of therapy, genetic changes in man and microorganisms, the immunologic process, and most commonly, the general increase in living standards. Tuberculosis is a social disease that is extremely sensitive to changes in the standard of living. The disease is an infection that is primarely spread directly from human being to human being. The degree of crowding and the standard of housing are therefore important factors when it comes to the spreading of the disease. Usually, steady contact is required in order that the disease should be transmitted. Tuberculosis is also sensitive to nutrition. Persons with good diets are far more resistant to the disease than those suffering from mal­nutrition or those with a poor diet. A protein deficiency is particularly dangerous. A reduc­tion of nutritional intake together with a greater degree of crowding should thus lead to an increase in tuberculosis in societies where the disease is endemic. On the other hand, a decrease in the tuberculosis frequency presupposes better standards of nutrition and housing, at least for the period prior to modern chemotherapy. Where diet and housing operate against each other, the frequency and occurence of tuberculosis functions as measure of the net result. Tuberculosis is a disease that shows clear symptoms in the lethal stage. The disease has been sufficiently widespread to permit statistical analysis even in small areas. This makes it possible to test the applicability of tuberculosis as an indicator of alterations in living standards. However, this presupposes that the effects of biological determinants can be accounted for. These biological determinants consist of both biological elements of the human body and changes in microorganisms. In this disseration, therefore, the following hypotheses are tested: —   that the extent of tuberculosis in a given society is governed by immunological processes resulting in an epidemic wave, —   that variations in the numbers of deaths from tuberculosis are an expression of changes in the standard of living. In addition to these hypotheses, the question is raised as to whether it is possible to measure deaths due to tuberculosis in historical populations with attention to each of the following: (1) changes in age and sex distributions; (2) possible changes in the virulence of the bacillus; and (3) also the results of changes in the degree of competition from other diseases. In the study, statistics for causes of death for counties, towns and parishes in northern Sweden were used together with parochial records and a number of other sources from seven parish districts with differing socio-economic structures. The thesis shows that tuber­culosis was endemic in both Sweden and Finland from about 1750. In Norrland, the disease was one of the most common causes of death. Thus, we can reject the hypothesis that the high tuberculosis frequency in Norrland during the 19th century was a result of a virgin population coming into initial contact with the disease. The regional distribution pattern and the rural/urban differences indicate a close relationship between different living standard factors. In the dissertation it is also shown that the age and sex structure was relatively constant during the period of study. Thus, we can reject the hypothesis of age transition. An age structure with an upper limit in youth is natural for the disease. The high level of tuberculosis in upper age strata during the 18th and early 20th centuries is seen as a residual effect of a higher tuberculosis mortality rate in earlier age cohorts. The major perspective is socio-economic, but the disease's histoire de mentalité has been treated . Popular beliefs concerning the disease and the attitudes formed in literature and in art — the myth-building that took place — is given particular treatment. The aim of this dissertation has been to investigate the relationship between bacilli, "human beings and society over a long period of time, 230 years. / digitalisering@umu