The spleen has an elongated, elliptical outline, both extremities being
thin, rounded, and similar in size.
Its average weight is about 30 ounces (ca. 800 to 900 gm.), or about ⅙
per cent. of the body-weight. Its length is about 16 to 20 inches (ca.
40 to 50 cm.), its width about 5 to 6 inches (ca. 12 to 15 cm.), and in
the middle its thickness is about an inch (ca. 2 to 3 cm.).
The =dorsal extremity= lies under the upper ends of the last two ribs;
the =ventral extremity= is usually opposite the seventh or eighth rib,
about a handbreadth above its junction with the cartilage. The =parietal
surface= is convex, and is related to the diaphragm. The =visceral
surface= is concave, and is related chiefly to the left face of the
rumen, but also usually to a narrow adjacent area of the reticulum. The
dorsal part is attached to the left crus of the diaphragm and the left
surface of the rumen by peritoneum and connective tissue; the ventral
part is free. The hilus is situated on the dorsal third of the visceral
surface, near the anterior border.
About one-half of the visceral surface of the spleen is attached
directly to the rumen and is not covered by peritoneum; the line of
reflection of the latter crosses the surface obliquely, from the upper
part of the posterior border to the anterior border a little below the
middle. Similarly there is a narrow uncovered area on the upper part
of the parietal surface along the anterior border. The hilus is not a
groove, but a simple depression. When hardened _in situ_, the organ is
seen to be somewhat twisted, so that the upper part of the parietal
surface faces upward and forward, while below it is directed outward.