"In vivo" uterine lumen pH values of the bovine.

The hydrogen ion concentration of the fluids of the uterine lumen was determined in six mature cows at 2 day intervals throughout the normal oestrous cycle. Determinations were made with a pH cardiovascular catheter electrode inserted into the uterus and a reference electrode placed externally over the sacrum of the cow. The grand mean of the determinations was pH 7.30. The pH changed with the period of the cycle. The lowest values occurred within 2 days prior to ovulation and a second low mean value occurred about 10 days following ovulation.