Introduction: Horizontal and Vertical Transmission of Diseases: the Impossible Separation Jean-Paul Gaudilliere and Ilana Loey Part 1: Tuberculosis 1. J. Andrew Mendelsohn Medicine and the Making of Bodily Inequality in Twentieth-Century Europe 2. Michael Worboys From Heredity to Infection? Tuberculosis, 1870-1890 3. JoAnne Brown Purity and Danger in Colour: Notes on, Germ Theory and the Semantics of Segregation, 1895-1915 Part 2: Etiology and Experimental Practices 4. Olga Amsterdamska Standardizing Epidemics: Infection, Inheritance and Environment in Prewar Experiemental Epidemiology 5. Jean-Paul Gaudilliere Making Heredity in Mice and Men: the Production and Uses of Animal Models in Postwar Human Genetics 6. Angela N. H. Creager and Jean-Paul Gaudilliere Experimental Platforms and Technologies of Visualization: Cancer as Viral Epidemic, 1930-1960 Part 3: Heredity, Medicine and Health Policies 7. Patrice Pinell Degeneration Theory and Heredity Patterns between 1850 and 1900 8. Patrick Zylberman Hereditary Diseases and Environmental Factors in the 'Mixed Economy' of Public Health: Rene Sand and the French Social Medicine, 1920-1934 Part 4: Transmission and Medical Practices 9. Paolo Palladino From Family Pedigrees to Molecular Markers: On Cancer and Heredity at St Mark's Hospital, 1924-1995 10. Jennifer Stanton and Virginia Berridge Vertical Ancestries and Horizontal Risks: Hepatitis B and AIDS 11. Ilana Loewy Predispositions, Cofactors and Images of AIDS Conclusion Jean-Pierre Revillard