The reticulum, which is the smallest of the gastric compartments, is situated in the sub-ensiform and retrodiaphragmatic regions, extending right and left of the middle line to a nearly equal distance. Above and to the left it communicates freely with the rumen, to the right with the omasum.
In practice it can only be examined in two ways: inspection and palpation.
By inspection changes in the configuration of the ensiform region may sometimes be detected. Such changes are rare, and must be distinguished from congenital deformity. They sometimes accompany inflammation of the reticulum produced by a foreign body, when the lower abdominal wall is directly perforated by such body.
In cases of inflammation of the reticulum due to foreign bodies, abscess formation, perforation, etc., it is possible to detect œdematous infiltration, abnormal sensibility, fluctuation and increased heat, etc., by manipulating the parts with the fingers or the clenched fist.
If the evidence pointing to the presence of a foreign body in the reticulum is considered sufficient, gastrotomy may be performed and the interior of the viscus examined with the hand, but although the operation is possible it is very rarely practised.
Omasum. The omasum occupies, so to speak, a position inverse to that of the reticulum, lying deep down on the right side, behind the diaphragm, under the hypochondrium, and above the abomasum and reticulum.
It is the only gastric compartment which cannot be examined, although when impacted it may be felt on the right side.
Abomasum. The abomasum is lodged in the lower part of the right flank under the circle of the hypochondrium. It extends obliquely from below, upwards from the sub-ensiform to the sublumbar region. The smaller curvature is turned towards the rumen on the left side; the larger curvature is in contact with the abdominal wall. In spite of what has so often been stated by those who have never seen it, the abomasum can be examined and is accessible along the circle of the hypochondrium.
In adults useful information can rarely be obtained by inspection; but in sucking calves the abomasum, if distended by indigestion, gastro-enteritis, etc., sometimes appears prominently in the right abdominal region. Palpation with the fingers or with the fist will detect exaggerated sensibility, irritation, inflammation, or distension.
Percussion and auscultation furnish no very precise information. The information obtained by the above-described examination of the stomach is in practice amplified by a search for certain symptoms which are usually easy to detect. They comprise: