opening (o'pen-ing). 1

The act of laying open (e. g., by making an incision or puncture); also the act of breaking an electrical current. 2. An orifice, a gap, a perforation. See aperture, apertura, foramen, ostium, and their subheadings. abdominal o. of the oviduct. The fimbriated extremity of the fallopian tube by which it communicates with the peritoneal cavity and applies itself to the surface of the ovary, anodal o. See under anodal. aortic o. The o. in the diaphragm which transmits the aorta and the vena azygos minor, cathodal o. The opening of a galvanic circuit attended with some phenomenon (e. g., muscular contraction) taking place at the cathode. Symbol, CaO or KaO. esophageal o. The o. in the diaphragm which transmits the esophagus and vagi, saphenous o. An oval o. in the fascia lat a, slightly below and external to the inner extremity of Poupart's ligament, which transmits the lateral internal saphenous vein. urinogenital o., urogenital o. The external o. of the genito-urinary tract.