The diagnosis, moreover, should be confirmed by making an aseptic exploratory puncture with the capillary trocar. The nature of the liquid withdrawn will indicate whether the case is one of simple acute pericarditis or pericarditis due to a foreign body.
Cancerous pericarditis is generally secondary, and is caused by development of tumours on the pericardial serous membrane, and in the myocardium. Moussu, however, has seen one case of primary cancerous pericarditis, the tumours being found only on the periphery of the myocardium. The growth assumes a vegetative form with moderate exudation. The symptoms, however, so closely approach to those of exudative pericarditis due to foreign bodies that only the latter variety, which is by far the most frequent in animals of the bovine species, need be described.
EXUDATIVE PERICARDITIS DUE TO FOREIGN BODIES.
Fig. 174.—Tumours of the surface of the heart. Primary cancerous pericarditis and myocarditis.
This condition has been erroneously described as traumatic pericarditis, but the latter term would suggest that the disease was due to an injury acting from without. It may be defined as a disease produced by the discharge into the pericardial cavity of some foreign body from the gastric compartments.
Boizy in 1858 described several cases of this kind of pericarditis. Hamon in 1866 gave an excellent table of symptoms. Roy in 1875 supplemented this with numerous observations showing clearly the possibility of recognising the disease by clinical examination. Pericarditis due to foreign bodies is to-day one of the best characterised diseases of the ox, and it is easy to diagnose.
Before approaching the etiological side of the question, it is necessary to recall in a few words the anatomical arrangement of the pericardium and its relations to neighbouring organs.
In the ox the diaphragm presents a marked concavity directed towards the abdomen. The pericardium, situated exactly in the median plane, is fixed by its point to the sternum. A fold of adipose tissue directly connects it with the anterior surface of the diaphragm. On the abdominal side the conical right compartment of the rumen is in free communication with the reticulum, which is closely applied to the posterior surface of the diaphragm on the median line opposite the spot occupied by the pericardium on the anterior surface (Fig. 176). As a result of this arrangement any object passing through the reticulum and diaphragm in the median plane would enter the pericardial cavity. These particulars indicate clearly how this form of pericarditis is produced.
Causation. One of the chief causes of pericarditis by a foreign body is connected with the way in which oxen feed. They rapidly swallow their food and any foreign bodies that may be concealed in it, submitting it later on to a second mastication in the course of rumination. This method of feeding results in bolting the food almost without mastication, hence the possibility of swallowing foreign bodies.