(a) The suprasternal plane, on a level with the disc between the second and third dorsal vertebrae.
(b) Ludwig's plane (junction of manubrium and gladiolus), on a level with the disc between the fourth and fifth dorsal vertebrae.
(c) The sterno-xiphoid plane (junction of sternum and xiphoid cartilage), on a level with the disc between the ninth and tenth dorsal vertebrae.
(d) The subcostal plane, on a level with the lower part of the third lumbar vertebra.
(e) The umbilical plane, on a level with the disc between the third and fourth lumbar vertebrae.
(f) The spinous plane, drawn between the two anterior superior iliac spines, and usually falling below the level of the sacral promontory.
The lineae semilunares correspond to the outer border of the rectus abdominis muscle, (Fig. XX, 12.) and extend, with a slight outward convexity, from the pubic spine below to the tip of the ninth costal cartilage above (the lateral central point).
The lineae transversae result from the tendinous intersections in the rectus abdominis muscle. (Fig. XX, 13.)
They are three in number, and are situated
(1) at the level of the umbilicus;
(2) midway between the umbilicus and the xiphoid cartilage;
(3) immediately below the xiphoid cartilage.
The semilunar fold of Douglas, representing the lower limit of the posterior lamella of the rectus sheath, (Fig. XX, 14.) lies about half-way between the umbilicus and the upper border of the pubic symphysis. The umbilicus usually lies 1 to 1 1/2 inches above the intertubercular plane, (Fig. XVIII.) and corresponds to the level of the disc between the third and fourth lumbar vertebras. The umbilicus is, however, so inconstant in position that the umbilical plane is rejected as often as possible in favour of a more definite and scientific plane.