Internal exploration is the only method of detecting changes in the thoracic portion, and may also be utilised to locate lesions in the cervical region. It is practised by passing a sound of small calibre or any flexible cylindrical object, such as a cart rope, etc. The patient must be fixed with the head extended on the neck and a proper gag or speculum introduced into the mouth. Exploration assists us in recognising the existence of inflammation of the œsophagus, true or false contraction, dilatation and the presence of obstructions.
In animals of the bovine species all these lesions—viz., inflammation of the œsophagus, fissuring and ulceration, obstructions, compressions, dilatations and contractions of the tube—although not very frequent, are nevertheless from time to time encountered.
Stomach. Exploration of the stomach or of the different gastric compartments presupposes an exact knowledge of the respective positions of the different reservoirs. Topographical anatomy shows that the rumen is situated in the left flank, and that it occupies the whole of the left abdominal region from the diaphragm to the pelvic cavity. As a consequence, it may be explored from the region of the twelfth rib; it is inclined slightly from above downwards, and from left to right, its extreme right border extending as far as, or a little beyond, the white line.
The reticulum, the smallest of the four reservoirs, is situated in the sub-ensiform region at right angles to the median plane of the body. On the left it touches the rumen and the diaphragm; on the right side it is in contact in front with the diaphragm, above with the omasum, and to the right and towards the rear with the abomasum. The omasum is situated above the reticulum and conical right portion of the rumen; in front it touches the liver, and towards the back and left the rumen. The abomasum is situated obliquely in the right hypochondriac region, its anterior surface resting on the lower wall of the abdomen towards the middle and right side of the body, its pyloric portion extending upwards, behind the right hypochondriac region.
Rumen. The rumen can be examined by inspection, palpation, percussion, and auscultation. The use of the œsophageal sound and of the trocar and canula is also of value in diagnosis.
Inspection affords information of a varying character, according to the moment when it is practised, even in a condition of health. It only extends to the condition of the flank before or after a meal, etc., emptiness of the rumen being accompanied by hollowness of the flank, and distension, following an abundant meal, by fulness in this region.
When digestion is not proceeding normally, the flank may be distended unduly by gaseous accumulations or by the presence of solid food. In abdominal and mediastinal tuberculosis and in gastro-enteritis there may be simple tension or slight dilatation. When indigestion or enteritis is entering on a favourable stage, the flank may appear hollow, and in cases of chronic diarrhœa it may appear retracted.
Fig. 60.—Position of the thoracic and abdominal viscera of the left side. A, posterior aorta; P, paunch or rumen; Id, line of insertion of the diaphragm; C, heart and pericardium; Pd, anterior lobe of right lung; Pg, left lung; D, diaphragm; Rg, left kidney.
Digital examination or palpation may be practised over the entire region of the flank. It shows whether the rumen is full or empty, reveals the consistence of the contained food in cases of chronic indigestion, the sensibility of the walls, and the rate and order of the muscular contractions. Direct or indirect percussion may be carried out on a horizontal line from the twelfth rib as far back as the flank, and vertically from the lumbar vertebræ to the white line. In health one discovers in young animals an upper zone of normal resonance due to gas, a zone of semi-dulness and an inferior zone of absolute dulness, due to the liquids in the rumen. The spleen, which is attached to the supero-anterior surface of the left side of the rumen, does not seriously restrict the area open to percussion.