Infectious Diseases And Traditional Medical Ideas About Inheritance. I. General Considerations.

Today, infection and inheritance are generally seen as medical opposites- environment vs. heredity. However, they actually influenced and supported each other well into the 20th century. Which category disorders belonged to wasn’t always clear, and the same rules could apply to both: Diseases could need both “seed and soil,” making them infectious and hereditary. Infections supported a medical alternative to genetics with variable traits with interacting causes, a view of what was inherited that undermined recognition of the distinct unit traits of Mendelian inheritance. This had four basic components that also applied to infectious diseases.: 1. Heredity as a force; 2. Degeneration, an often progressive weakening of that force; 3. Diatheses (predispositions); and 4. Polymorphism- variable entities that could transform into one another. Successes against infectious diseases changed medical experiences, undermining non-Mendelian ideas. With this, genetic concepts became increasingly dominant in medicine, and separate from infections.