Pericarditis, more especially when of a chronic form, is important in reference to the origins of the large vessels. It would seem, according to our view, that this disease, as far as it affects the cellular sheath of the vessels in the sub-serous cellular tissue, must induce paralysis of the elastic coat, dilatation of the aorta, and that form of spontaneous laceration of the vessels within the pericardium, which is so often found to occur.

3. Pericarditis frequently occurs in original combination with inflammation of other serous sacs, as for instance with pleuritis, inflammation of the synovial membranes of the large joints (Bouillaud), and very frequently with pneumonia. It is, moreover, in like manner associated with endocarditis, and occasionally with carditis: during the later stages it is often accompanied with the first-named inflammatory processes, and also with meningitis.

Pericarditis is often a secondary aifection associated in various degrees of intensity with other processes of exudation, and very frequently a slight reddening, injection, and an inconsiderable degree of effusion, are found to attack the pericardium at periods of complete exhaustion, and in consequence of extensive exudations. Acute pleurisies extend from the mediastinum to the pericardium, and centres of inflammation in the muscular tissue of the heart sometimes occasion general and sometimes partial inflammation of the pericardium.

Pericarditis, contrary to the results of the investigations of many observers, is frequently met with beyond the middle periods of life and even in advanced age.

B. Secondary Formations

1. Adiposity Of The Pericardium

We not unfrequently observe an excessive accumulation of fat on the pericardium. This occurs in general not only in conjunction with an excess of fat in the heart itself, but also together with fatty accumulations in the abdomen, that is to say in the great omentum and its appendages, in the mesentery, under the costal pleura, etc, constituting a general condition of corpulence.

2. Fibroid Tissue

Fibroid Tissue occurs in the milk-spots and in the fibroid granulations, assuming the form of a thick exudation, having the property of resistance, and being of a very dense texture.

3. Anomalous Osseous Substance

Anomalous Osseous Substance is scarcely ever developed, excepting in the above-named fibroid exudation, after the lamellae have become fused together, and the pericardium has thus been made to adhere to the heart by this dense and resisting fibroid medium. This adhesive stratum is now covered by a deposit of tuberous uneven laminae and bands, or thick, roundish, nodular masses. The space occupied by the deposits varies considerably, but the first-named of these forms of deposition occasionally extends so far as to cover the greater portion of one ventricle. The projections occupying the side next the heart frequently extend to the texture of the heart itself, displacing the muscular bundles, and appearing as if developed within them. The thick, round, nodular masses are generally observed in the neighborhood of the sulcus transver-salis on the left side of the heart, being connected with an osseous concretion which usually has its seat at the margin of insertion of the mitral valve. They are consequences of a former state of endocarditis combined with pericarditis.