Abstract:
In 201 of 212 oestrous cycles in 25 adult Merino ewes a fairly uniform sequence of changes occurred in the macroscopic nature of the vaginal contents. This sequence of changes or 'vaginal cycle' was characterized by the presence of mucus, frequently in great amount, during oestrus, and the appearance of quantities of material of a cheesy consistency within 3 days following oestrus. The cheesy material usually persisted for 3 or more days and was succeeded by small amounts of material of a semitransparent or clear serous nature. Two or three consecutive vaginal cycles occupied 32 interoestrous intervals of 31-61 days, most of which occurred during well-defined sexual seasons, and in two instances consecutive vaginal cycles continued throughout the whole of the interval between two well-defined sexual seasons. Some vaginal cycles also occurred during most other anoestrous intervals between sexual seasons. Forty oestrous periods were either associated unusually with a vaginal cycle or were not associated with any regular sequence of changes at all. Twenty-one of these periods occurred at the beginning or during the course of periods of reduced sexual activity.