We may divide the above into Diseases of the Heart, including those of the Pericardium, and Diseases of the Arteries, the Veins, and the Lymphatics. Under the last head are included Diseases of the Lymphatic Glands.

1. Deficiency And Excess Of Formation

The first-named species of malformation manifests itself as a deficiency of the pericardium, occurring generally when the heart lies outside the thorax, although it is also met with when this anomaly is not present; but is then of less frequent occurrence. This deficiency is in almost every instance merely partial, consisting in the congenital anomalous position of the heart outside the thorax in a fissure of the pericardium, although it is not uncommon in some cases to meet with less marked traces of the same condition in the region of the larger arterial trunks and along the right layer of the mediastinum. The heart and the left lung lie, as a general rule, in one common large serous sac, which gives rise, at the place from whence the arterial trunks emanate, to the above-mentioned rudiments or traces, in the form of fatty mesentery-like folds.

The apparent deficiency of structure, induced by the firm adhesion of the pericardium to the heart, seems to have been mistaken by some older observers, for true deficiency of structure.

An Excess of Formation occurs in double monsters, where the pericardium is found to contain a double heart.

2. Deviations In Size And Form

The size and form of the pericardium depend originally upon the size and form of the heart; and likewise, although in a less degree, upon the calibre, number, and arrangement of the vascular trunks springing from the heart.

An acquired dilatation of the pericardium frequently occurs in consequence of an increase of the heart's volume, or of dilatation of the vascular trunks, especially of the aorta, and very commonly from morbid effusions, as for instance, the formation of inflammatory products in its' cavity. In these cases the dilatation of the pericardium is uniform, and frequently, as in exudations, and more especially in enlargement of the heart, it is so considerable that the pericardium may extend in a diagonal direction from the anterior extremity of the second or first rib on the right side to that of the eighth rib on the left side, having its anterior surface pressed againt the sternum and the costal cartilages-reaching on both sides to the lateral walls of the thorax, and compressing the lungs, especially their lower lobes, in the posterior part of the thoracic cavity.

Moreover, in some few cases, a partial dilatation of the pericardium also occurs as a Diverticulum or Hernia Pericardii. This is in fact a hernial dilatation, occasioned by the penetration of the serous surface of the pericardium through different non-resisting or ill-protected parts of the fibrous layer, or through apertures in this layer, expanding into an appendage, which is attached to the pericardium by a pedicle or neck, and communicates with it by means of a narrow opening or canal.

Our museum contains two very instructive cases of the development of Hernia Pericardii; in these the diverticula are seated on the lateral parts of the pericardium. Hart's case affords an important example of the attachment of a large appendage to the anterior portion of the pericardium.

3. Interruptions Of Continuity

To these appertain injuries inflicted by various penetrating instruments, and by the impaction of fragments of the sternum or the ribs; lacerations from severe concussions or contusions of the body; ulcers perforating from without inwards, etc.