Experimentation with the "in vitro" methodology allowed the authors to study the effects of several pharmacological substances on human and animal tissue, making possible a qualitative assessment of activity, the quantitative dose-response relationships, the possible existence of specific drug receptors and the action, competitive or non-competitive, of a given antagonist. This methodology was applied to perinatology, particularly to two types of tissues: umbilical and placental vessels, arteries and veins; human and animal myometrium. Among the known circulating vasoactive substances, the authors obtained helpful results with the use of morphine, with obvious implications in obstetrical practice, that opioid substances very frequently are used to control the pains of childbirth. The experimentation with alcohol on isolated umbilical arteries and veins helps to explain the fetal alcohol syndrome. Finally, the study "in vitro" on human and animal myometrial strips gave interesting cues for the research into the regulation of the uterine contraction.