When theory and evidence disagree it becomes necessary to revise our teaching in favor of the evidence. Such a situation exists in reference to the dilatation of the cervix uteri in labor and the role of the amniotic sac. The exaggeration of the dangers of dry labor, based on hypothetic considerations, has a pernicious effect in that (1) the physician, in common with the public, often overlooks and neglects the real cause of a dystocia once it is ascribed to the "dry labor," and (2) the diagnosis of dry labor, if it is viewed as a complication, often impels the physician to unwarranted and dangerous interference with what is merely a slow parturition.
The fault lies in the older teaching only just now being corrected to some extent in the latest textbooks. Carefully controlled observations of the last fifteen years, as reported by more than a score of different obstetricians,