plane

(plan) [L. pia’nus]. A flat surface. Add is on’s p’s, planes used as landmarks in the topography of the thorax and abdomen. Aeby’s Ῥ., a plane through the nasion and basion, perpendicular to the median plane of the cranium. auriculo-infra-orbital p., a plane pa ing through the auricular points and the lowest points of the orbits. Baer’s p., a plane through the upper border of the zygomatic arches. Blumenbach’s p., a plane parallel with the base of a skull from which the lower jaw has been removed. datum p., a given horizontal plane from which craniometric measurements are made. Daubenton’s p., a plane in which are the opisthion and the lower edges of the orbits. Hensen’s p., a plane pa ing through the center of a series of sarcous elements of a muscle-fibril. Hodge’s p., a plane pa ing through the second sacral vertebra and the upper border of the os pubis, and parallel to the plane of the pelvic inlet. Listing’s p., a transverse vertical plane which is perpendicular to the anteroposterior axis of the eye, and which contains the center of motion of the eyes; in it also lie the transverse and vertical axes of voluntary ocular rotation. Meckel’s p., a plane pa ing through the auricular and alveolar points. Morton’s p., a plane through the most projecting points of the parietal and occipital protuberances. nuchal p., the outer surface of the occipital bone between the foramen magnum and the superior curved line. occipital p., the outer surface of the occipital bone above the superior curved line. orbital p. 1. The orbital surface of the maxilla. 2. The plane that pa es through the visual axis of each eye. popliteal p., the popliteal space. tal p., a plane running in an anteroposterior 144 PLASMAPHERESI!S direction. sternal p., the anterior surface of the sternum. tentorial p., a straight line drawn through the tentorium. visual p. Same as orbital p. (2d def.).