Dr. Baillie, speaking of inflammation of the substance of the heart, says, "When the pericardium covering its surface is inflamed, the inflammation sometimes passes a little way into the substance of the heart:" and then he gives these as the characteristic marks of such inflammation--that "it (the substance of the heart) becomes much more crowded with small vessels than in its natural state, and there are sometimes to be seen a few spots of extravasated blood." Now, this undue vascularity, and these few extravasated spots, where inflammation unquestionably belongs to a contiguous structure, may be deemed sufficient evidence of the muscular substance of the heart participating, or beginning to participate, in the same disease; but, absolutely and exclusively, it may be doubted whether more is not required to give a certain assurance of its inflammation. Here, as elsewhere, we must look for some of the proper products of inflammation; or for some of the permanent changes of texture which naturally result from it, according to its several modes of disorganizing. It is a very rare event to find pus among the products of inflammation of the substance of the heart: yet this event has occurred twice to my observation. In one instance the whole heart was deeply tinged with dark-coloured blood, and its substance softened; and here and there, upon the section of both ventricles, innumerable small points of pus oozed from among the muscular fibres. This was the result of a most rapid and acute inflammation, in which death took place after an illness of only two days. In another instance, after death, which terminated an illness of long duration and characterized by symptoms referable to the heart, a distinct abscess was found in the substance of the left ventricle, closed externally by a portion of adherent pericardium, and connected internally with an ossified portion of the lining membrane. This diffusion of pus, or rather its formation in innumerable separate points, throughout the muscular structure of the heart, by a rapid and acute inflammation, is a singular occurrence. No such case has ever fallen within the knowledge of the most experienced in morbid anatomy, of whom I have made inquiry; neither has any such (as far as I can learn) been recorded in books[10]. A single collection of pus[11], constituting an ulcer or abscess of the heart, and resulting from chronic inflammation, is also a rare occurrence, yet not so rare but that a specimen of it may be found in most collections of morbid anatomy[12]. But independent of the formation of pus, softening and attenuation, as well as induration and thickening of the muscular substance of the heart, do, in different cases, according to the circumstances under which they are found, both bespeak inflammation.