c. These vegetations on the valves - in perfect analogy with other fibrinous coagula - undergo, although less directly, a bony and chalky metamorphosis, constituting a special form of valvular ossification, to which we will revert in the sequel.

d. These vegetations seldom, and indeed never, unless when of considerable dimensions, experience that metamorphosis of softening, by which a fibrinous coagulum is converted into a hollow globular vegetation. This metamorphosis, which occurs in the early stages of recent vegetation, is undoubtedly the result of extensive diseases of the fibrin.

In conformity with their elementary character they consist, according to their respective ages, of elementary granules, cell-nuclei, and cells - of a homogeneous base, intersected by nucleated fibres, in the manner of the longitudinal fibrous coat - of fibres and fibrillse resembling cellular tissue, and of thick tubular fibres.

The corresponding opening is more or less closed, in proportion to their number and volume.

In all considerations that relate to the origin of these vegetations we ought, in the first place, to notice their relation to the endocarditic process.

In the greater number of cases these structures are accompanied with the phenomena of endocarditis - the alterations of texture to which it gives rise; their appearance so far coinciding with these phenomena, that recent vegetations are found simultaneously to occur with recent derangements of texture, and obsolete vegetations with inveterate disturbances of texture - the residua of endocarditis. The question here arises in relation to these cases, are these vegetations endocarditic exudations? and if not, how can their origin depend upon the process of endocarditis?

In some rare cases they are observed unaccompanied with any phenomena of endocarditis; and here it may be asked, how is their origin to be explained, and on what does it mainly depend?

The result yielded by very numerous and widely differing cases are as follows: a. That these vegetations, when considered collectively, are in some cases, direct products of inflammation - that is to say, exudations.

b. That in the great majority of cases they are only in part to be regarded as inflammatory products, since it is only the lowest layer, directly adhering to the excoriated valve, that can be considered in the light of an exudation, whilst the greater number have been produced in another indirect and secondary manner from the endocarditis.

c. That they also occasionally occur without the existence of endocarditis.

In the two latter cases, the vegetations occur as fibrinous coagula deposited by the blood, and their formation is effected in the following indirect and secondary manner:

Endocarditis induces a diseased condition of the blood, in consequence of the latter taking up its exudations. This morbid state is manifested by the readiness with which its fibrin coagulates and separates. As such coagula occur in different parts of the capillary system (as secondary processes in the spleen and kidneys), so also is the fibrin separated from the blood in the heart with a readiness proportional to the vegetations produced by the endocarditic process in the form of exudations, or the number of loose, rough, felt-like excoriated spots on the endocardium, either of which may exert a mechanical action.

The number and dimensions of these secondary vegetations accord with the intensity of this disease of the blood, and more especially with its character; and we find that they occur in the most exuberant masses when there is intense endocarditis, manifested by simultaneous disturbances of texture, and still more so where the disease is characterized by suppuration. This correspondence is further manifested in a remarkable manner by the great number of secondary processes in the different parenchymatous structures to which we have referred. The mechanical influence is more developed in proportion to the greater intensity of the endocarditic process. The number of vegetations is, however-most remarkable on the margins of a fissure in the endocardium and in the subjacent tissues, occasioned by inflammatory loosening of the texture, or still more, perhaps, by suppuration. It is obvious that the number of these vegetations increases with the extension of the endocarditis, and of the space over which the mechanical influence has diffused itself.

The metamorphosis of all these vegetations generally, and of those of the second form especially, depends upon an internal cause (namely the blood). Where, as is usually the case, the product deposited is of a benignant nature, the fibrin constituting these vegetations experiences the above-named favorable modifications, that is to say, the vegetations become condensed, gradually diminish, and even wholly disappear, or cre-tify. This is in accordance with such terminations as shrivelling, obliteration, and atrophy, which usually characterize the secondary process accompanying such an endocarditis. In some less frequent cases the vegetations undergo a softening process, and become diffluent in their interior, yielding a variously colored purulent fluid. This is observed in intense endocarditis, and when it occurs with purulent exudation, and in this respect it also agrees with those secondary processes of a less benignant character which terminate in purulent fusion. These metamorphoses are more commonly manifested in vegetations consisting of a large club-like villi or roundish masses, which, as we have already observed, accompany intense endocarditis, characterized by purulent exudations. The vegetations that begin to dissolve at the centre approach more nearly to the character of the globular kind in proportion to the roundness of their form.