The Anatomy of the Human Peritoneum and Abdominal Cavity: Considered from the Standpoint of Development and Comparative AnatomyHuntington, George S. (George Sumner)
Science
The Anatomy of the Human Peritoneum and Abdominal Cavity: Considered from the Standpoint of Development and Comparative Anatomy
Huntington, George S. (George Sumner)
Abdomen; Peritoneum
There are here two large reservoirs, which correspond to the rumen and
retinaculum of the ruminants, and a digestive compartment containing
gastric glands, which corresponds to the ruminant abomasum, and is
connected by an oesophageal gutter directly with the oesophagus. At the
pyloric extremity the muscle wall is greatly increased and the mucous
membrane of this portion carries a thick horny covering, forming a
masticatory stomach greatly resembling the corresponding structure in
the bird. Its function is evidently to complete the mechanical division
of the food which has only been partly masticated in the mouth.
The same significance is probably to be attached to the thickened
muscular walls which the pyloric segment of the stomach in _Tamandua
bivittata_, another edentate, presents (Fig. 96), in strong contrast
with the thinner walled cardiac segment and fundus.
[Illustration: FIG. 96.--Stomach of _Tamandua bivittata_, collared
ant-eater, (Columbia University Museum, No. 68/1485.)]
INTESTINE.
Continuing our consideration of the development of the alimentary canal
we find that changes from the simple primitive straight tube below the
stomach depend upon two factors:
1. The increase in the length of the intestinal tube, which exceeds
relatively the increase in the length of the body cavity in which it is
contained.
2. The differentiation into small and large intestine, the development
of the caecum and ileo-caecal junction, and the development of the
accessory digestive glands, liver and pancreas, by budding from the
proximal portion of the primitive entodermal intestinal tube.
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