\Germ theory\
1. (Biol.) The theory that living organisms can be produced
   only by the development of living germs. Cf. {Biogenesis},
   {Abiogenesis}.
2. (Med.) The theory which attributes contagious and
   infectious diseases, suppurative lesions, etc., to the
   agency of germs. The science of bacteriology was developed
   after this theory had been established.