secular changes in seasonal periodicities are investigated and these are associated with other changes , such as the intrinsic periodicities , mode of spread , etc. , the combined changes being described by the terms aggradation and degradation of disease.slides covering the majority of the infective diseases of temperate climates and exhibiting the secular changes in liverpool , and various geographical differences , in some 175 curves displayed .
C0012634
disease
C0009450
infective diseases