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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
recedes above the margin of the ribs and cannot then be detected by the finger; in the prone position it falls forward and is then generally palpable in a patient with loose and lax abdominal walls. Its position varies with the respiratory movements; during a deep inspiration it descends below the ribs; in expiration it is raised. Pressure from without, as in tight lacing, by compressing the lower part of the chest, displaces the liver considerably, its anterior edge frequently extending as low as the crest of the ilium. Again its position varies greatly with the state of the stomach and intestines; when these are empty the liver descends, when they are distended it is pushed upward.
  The pancreas can sometimes be felt, in emaciated subjects, when the stomach and colon are empty, by making deep pressure in the middle line about 7 or 8 cm. above the umbilicus.
  The kidneys being situated at the back of the abdominal cavity and deeply placed cannot be palpated unless enlarged or misplaced.
 
8. Surface Markings of the Abdomen
 

Bony Landmarks.—Above, the chief bony markings are the xiphoid process, the lower six costal cartilages, and the anterior ends of the lower six ribs. The junction between the body of the sternum and the xiphoid process is on the level of the tenth thoracic vertebra. Below, the main landmarks are the symphysis pubis and the pubic crest and tubercle, the anterior superior iliac spine, and the iliac crest.

Muscles (Fig. 1227).—The Rectus lies between the linea alba and the linea semilunaris; the former is indicated by the middle line, the latter by a curved line, convex lateralward, from the tip of the cartilage of the ninth rib to the public tubercle; at the level of the umbilicus the linea semilunaris is about 7 cm. from the middle line. The line indicating the junction of the muscular fibers of Obliquus externus with its aponeurosis extends from the tip of the ninth costal cartilage to a point just medial to the anterior superior iliac spine.
  The umbilicus is at the level of the fibrocartilage between the third and fourth lumbar vertebræ.
  The subcutaneous inguinal ring is situated 1 cm. above and lateral to the public tubercle; the abdominal inguinal ring lies 1 to 2 cm. above the middle of the inguinal ligament. The position of the inguinal canal is indicated by a line joining these two points.

Surface Lines.—For convenience of description of the viscera and of reference to morbid conditions of the contained parts, the abdomen is divided into nine regions, by imaginary planes, two horizontal and two sagittal, the edges of the planes being indicated by lines drawn on the surface of the body (Fig. 1220). In the older method the upper, or subcostal, horizontal line encircles the body at the level of the lowest points of the tenth costal cartilages; the lower, or intertubercular, is a line carried through the highest points of the iliac crests seen from the front, i. e., through the tubercles on the iliac crests about 5 cm. behind the anterior superior spines. An alternative method is that of Addison, who adopts the following lines:
  (1) An upper transverse, the transpyloric, halfway between the jugular notch and the upper border of the symphysis pubis; this indicates the margin of the transpyloric plane, which in most cases cuts through the pylorus, the tips of the ninth costal cartilages and the lower border of the first lumbar vertebra; (2) a lower transverse line midway between the upper transverse and the upper border of the symphysis pubis; this is termed the transtubercular, since it practically corresponds to that passing through the iliac tubercles; behind, its plane cuts the body of the fifth lumbar vertebra.

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