Observations on the spontaneous motility of human uterine muscle in vitro

1. 1. The capacity of human uterine muscle for spontaneous shortening was found to decrease with age, and the activity of myometrial samples from old, postmenopausal women was characterized by relatively rapid, feeble contraction waves. 2. 2. Myometrial samples excised from uteri with secretory endometria exhibited a slower rate of spontaneous motility than did those from uteri in the proliferative phase. Muscle shortening, however, was found to be unaffected by the ovarian cycle. 3. 3. Repeated pregnancies and labors, the presence of leiomyomas else-where in the uterus, sedatives, analgesics and anesthetic agents administered at the time of operation, as well as race, were found to be of no statistical significance as factors influencing the spontaneous motility of myometrial strips excised from the nongravid human uterus. 4. 4. Muscle samples removed from gravid uteri (from 2 months' gestation until term) exhibited no statistical differences in regard to motility, when compared with tissues from the nongravid viscus. 5. 5. In a limited number of tests, myometrial tissues from patients with primary uterine inertia exhibited a significantly reduced muscle shortening with increased frequency of contraction when compared with “normal” tissues from both nongravid and gravid uteri.