(1) Twenty-five beef heifers were subjected to delayed breeding up to ages
varying from four years to five years eight months.
(2) Observations on body-weights, age of sexual maturity, the periodicity and
duration of oestrus and the results of mating are recorded.
(3) Seven heifers bred successfully, while the remainder showed extensive
disturbances in sexual activity.
(4) The changes occurring in the genital tract during the normal sexual cycle
and during pregnancy are described.
(5) Profound functional and structural changes were observed in the genitalia
of the majority of animals, leading to abortion, functional sterility, nymphomania
(6) Correlative macroscopical and histological changes were observed in the
anterior pituitary, thyroid and adrenals of normal and affected animals.
(7) The genesis of sterility in relation to delayed breeding in the light of
the structural and physiological alterations observed, is discussed.