*germ theory*

. 1. (Biol.) The theory that living organisms can be produced only by the development of living germs. Cf. Biogenesis, Abiogenesis. [ Webster 1913 Suppl. ]

2. (Med.) The theory which attributes contagious and infectious diseases, suppurative lesions, etc., to the agency of germs, i.e. pathogenic microorganisms. The science of bacteriology was developed after this theory had been established. [ Webster 1913 Suppl. +PJC ]