The Milk Spots, Or Maculae Albidoe, are appearances of frequent occurrence on the heart. They are occasionally met with on the inner surface of the pericardium, but most frequently on the serous investment of the heart. There can scarcely be a question but that they are products of a partial or circumscribed process of inflammation. They are pale, bluish-white, tendinous-looking spots or plaques, appearing, when closely investigated, to be glued or soldered to the subjacent tissue; on being torn or detached, the pericardium is brought into view, and is almost normal in its character, - not perfectly smooth, but having a dense and sometimes even an opaque tissue. They must be distinguished from many other diffuse opacities of common occurrence on the pericardium, which consist in an inconsiderable excess of structure, - hypertrophy, a slight thickening and condensation of the serous investment of the heart. They further manifest many different characteristics with respect to their size and distribution, the number in which they occur, their form and limitation, the surface and mode of attachment; finally, they occur more frequently on some portions of the heart's surface than on others.

The size of these spots varies from that of a silver groschen or a narrow stripe, or that of a silver thaler or more, so that one spot often spreads over a great portion of the heart's surface. A number of these spots are often found together, and they then blend into one another. Their form varies very much, and is extremely irregular; they commonly occur as narrow stripes along the coronary vessels in the sulcus longitudinalis. They usually expand into linear projections at their periphery, and are either sharply defined, or gradually attenuated into a very delicate membrane, as may be seen in moist preparations. Their surface is either smooth, even, serous and shining, or wrinkled, folded, pale, felt-like, and shaggy; the whole presenting a layer of newly-formed cellular tissue.

These milk-spots occur on every portion of the heart, but they are certainly more frequent on the right than on the left ventricle; they usually appear on the auricles in the form of stripes, and finally are met with at the origins of the arterial trunks, and more especially at that of the aorta.

In connection with the subject of milk-spots, we may notice the metamorphosis of a partial exudation into fibroid granulations, occurring about the size of a millet-seed. These are especially to be met with on the auricles, and on the corresponding portion of the parietal surface of the pericardium. Granulations of this nature are frequently situated on these spots.

Inflammations with purulent exudation are distinguished by the quantity of the effusion, and are important on many accounts, which will be subsequently considered.

Scattered accumulations of pus are of very frequent occurrence in the subserous layers of the pericardium.

It is only in very rare cases that the purulent exudation leads to suppuration of the pericardium.

Our museum presents an instance of an originally sero-purulent exudation, which appears to have gradually undergone the following remarkable metamorphosis. At the circumference of the left side of the heart, the pericardium is closely adherent, whilst a whitish, very turbid fluid resembling milk of lime is accumulated around the right side of the heart. The inner surface of the pericardium, and more particularly the outer investment of the heart, appear partially encrusted as with a sandy mortar, and partly covered with a white, smooth, gypsum-like coating.

Among the chronic inflammations those attacking the pseudo-membranes are especially frequent and important; here we find peripheral coagula of very considerable thickness, density and power of resistance, and of a fibroid texture; the pericardium itself acquires a considerable degree of thickness, and in cases where there is a resorption of the fluid, the two lamellae of the peripheral coagula adhere together, and the heart becomes enclosed in a thick, tough, unyielding casing. Hemorrhage very generally accompanies the secondary exudations in this process.

Finally, when the necessary conditions are present, the exudation may be tuberculous; but this subject will be noticed when we proceed to the consideration of tuberculosis of the pericardium.

In every form of pericarditis the pericardium may become very much distended, in consequence of the great quantity of the exudation, and especially of its serous portion.