Second stage. Puncture with a sharp trocar directed forwards, downwards, and inwards. In making this puncture the point of the trocar is passed through the incision, and a sharp push is given. The sensation of resistance overcome indicates that the trocar has penetrated the cavity of the rumen. Gas then escapes. When the operation is completed, and the canula is being withdrawn, care should be taken to press down the skin on either side with the fingers of the left hand, to prevent accidental lifting and laceration of the connective tissue. Even so slight an accident as this might cause serious complications at a later stage.
In the absence of a trocar, and in cases of extreme urgency, the rumen may be directly punctured with a straight bistoury, and after the punctured wound is slightly enlarged, but before the blade of the bistoury is withdrawn, an improvised canula, consisting of a hollow elder twig, may be introduced. Were the blade of the bistoury withdrawn before the introduction of the canula, the rumen would be displaced, and the points punctured would no longer correspond.
Complications, such as respiratory or circulatory syncope, attacks of vertigo, etc., have been noted, but these in reality are very rare.
Subcutaneous Emphysema.—When the canula is carelessly removed, and the subcutaneous connective tissue is torn, local emphysema may occur if the pressure of gas in the rumen is very great. This gas enters the puncture, proceeds along the connective tissue, particularly the subcutaneous connective tissue, and causes crepitant subcutaneous emphysema, very easy to recognise. This emphysema may remain localised in the neighbourhood of the puncture and gradually become absorbed. It may, however, extend to the whole of the flank or even beyond, and in exceptional cases bring about generalised subcutaneous emphysema. Such very extensive emphysema as this rarely becomes reabsorbed without complications.
The suppuration which follows puncture of the rumen may assume one of two forms:—
(a) That of a little local abscess at the point of puncture, when foreign matter or the microbes of suppuration have been left in the path made by the withdrawal of the canula. Such abscesses are of little importance. They rapidly heal if opened and treated with antiseptic injections.
(b) That of diffuse subcutaneous or interstitial suppuration following accidental emphysema.
The pressure of gas forces fragments of food material between the layers of tissue, and suppuration is set up, the pus escaping by a fistula at the point of puncture. Such suppuration is decidedly dangerous, because it may result in necrosis of the aponeurotic layers of the small oblique muscle, in which case recovery is tedious and uncertain.
Treatment consists in laying open the orifice and fistula, and making a counter-opening at the lowest point of the swelling. Free drainage and abundant irrigation with boiled water at the body temperature, followed by antiseptic injections, complete the treatment.
Peritonitis is not altogether exceptional as a sequel to puncture of the rumen, if ordinary precautions are neglected or if infective material or fragments of food pass into the peritoneal cavity.