The cavity having been drained, a long strip of iodoform gauze is introduced into the track and a protective surgical dressing applied over the incision in order to prevent infection by the litter.
In consequence of the introduction of the fingers into the track caused by puncture and the escape of pericardial liquid along the canula or after removal of the canula, the operative wound is necessarily infected; but this is of little importance, because the opening is inclined downwards, and also because it is impossible to hope for aseptic healing.
The dressing is renewed after forty-eight hours, and every three or four days afterwards.
The œdematous infiltration about the front portion of the body disappears rapidly in two to three days, and should the animal be slaughtered the meat is quite sound in appearance.
This operation does not aim at effecting a cure, but is simply for the purpose of allowing animals which would otherwise be valueless to be slaughtered and sold.
Fig. 180.—Photograph of the same subject as Fig. 179, taken six days later.
CHRONIC PERICARDITIS.
Pericarditis when due to tuberculosis may assume the chronic form. Tuberculous pericarditis, at least in a large number of cases, is only accompanied by slight exudation, which might remain unnoticed unless the animals were carefully examined; but it causes the internal surface of the pericardial sac and the surface of the myocardium to become covered with exuberant vascular growths, which by setting up adhesions lead to partial or generalised union of the heart and pericardial sac. Between these adhesions, which form partitions, are found little cavities filled with sero-sanguinolent, grumous, or caseous liquid. In time the adhesions increase in number, pericarditis obliterates the free space, and the heart becomes wholly adherent to the pericardium.
As in acute pericarditis, the fibrous layer undergoes thickening and hardening processes. The superficial layers of the myocardium undergo sclerous transformation, and the tissues forming the adhesions themselves may assume the characters of fibrous tissue.