ZYMOTIC DISEASES (Gr. vµ7, ferment)  , a

term in medicine, formerly applied to the class of acute infectious maladies . As originally employed by Dr W . Farr, of the British Registrar-General's department, the term included the diseases which were " epidemic, endemic and contagious," and were regarded as owing their origin to the presence of a morbific principle in the system, acting in a manner analogous to, although not identical with, the process of fermentation . A large number of diseases were accordingly included under this designation . The term, however, came to be restricted in medical nomenclature to the chief fevers and contagious diseases (e.g. typhus and typhoid fevers, smallpox, scarlet fever, measles, erysipelas, cholera, whooping-cough, diphtheria, &c.) . The science of bacteriology has displaced the old fermentation theory, and the term has practically dropped out of use .