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(vertebrate zoology)
The third chamber of the ruminant stomach where the contents are mixed to a more or less homogeneous state. Also known as manyplies; psalterium.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



one of the glandless sections in the multicompartmental stomach of ruminants (it is not present in Tragulidae and camels), located between the reticulum and abomasum. The mucous coat on the inner surface of the omasum, except for on the bottom, forms longitudinal folds of varying heights, or laminae that are similar to the pages of a book (hence the Russian name knizhka, literally “book”). These laminae are mobile, since they have smooth muscle. Thus, the cavity of the omasum is divided into narrow chambers and only at its base, which the free ends of the laminae do not reach, is there an integral cavity, the canal of the omasum. In the omasum the feed that has been swallowed again by the animal after rumination is finally ground down and converted into a gruel-like substance that passes into the abomasum. Along the bottom of the omasum there is an abomasal groove, the sulcus omasi, serving as a direct continuation of the reticular groove; liquified food can flow along it directly into the abomasum.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The yak stomach consists of four parts, each with its own morphological particularities, including rumen, reticulum and omasum, known as forestomach (Hofmann, 1973).
Caption: Figure 3: a-d: Micrograph of bovine omasum after treatment with 0.5% of TnB at 12, 24, 48 and 72h (H&E Stain, 100X)
It appears to be most important in preweaned ruminants, allowing milk to avoid the immature reticulum and rumen and move directly to the omasum and on to the abomasum (Figure 2-5).
George Sun, Chairman of Jinan Kemp International Trading Company intending to import 200 containers of Omasum every month from Pakistan.
Also, I was using tripe (Omasum) in my work, and so vernacular phrases used by butchers to describe the third stomach of the cow as 'the bible' because of its delicate leaves of a book-like structure took on an extra meaning.
For g.33185918G>A, the G-bearing genotypes (GA heterozygotes or G allele homozygotes) were associated with a greater weight of the rumen, omasum and testes and a higher fat color score (7.480.91 kg, 3.940.59 kg, 0.690.13 kg, and 2.970.74, respectively) than the AA genotype, which was related to a higher pH of beef (5.910.78 kg) (Pless than 0.05, Table 3).
Roughage quality had no effects on wet digesta load (rumen and abomasum) and dry digesta load (omasum and abomasum) (Table 8).
The following body components were also weighed: head, skin, feet/ankles, tail, testicles, mammary gland, trachea/ esophagus, lung, heart, liver, bladder, diaphragm, spleen, pancreas, kidneys, rumen/reticulum, omasum, abomasum, small intestine and large intestine.
The right and left halves of the warm carcass, hide, head, blood, shanks and tail, liver, heart, lung, kidneys, spleen, rumen-reticulum, omasum, abomasum, small and large intestine and internal adipose tissues were weighed and recorded after washing to obtain the empty body weight (EBW).
Diseases of the rumen reticulum and omasum. In: Veterinary Medicine - A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goats, 10th Edn.
Larger particles of food that pass through the reticulo-omasal orifice are retained between the omasum's folds, with fluid components being transported comparatively rapidly to the abomasum.