The simple coagulum met with in the heart or great vessels after death, and in blood drawn from bloodvessels during life, furnishes the chief groundwork for this inquiry.

These coagulations, which vary essentially, both as to external appearance and to elementary constitution, form the basis of the different qualitative fibrin erases. We should, however, begin by stating that the individual forms seldom, if ever, occur in their perfect simplicity, owing both to the mutable nature of the substance, and to the fibrin not becoming throughout equally influenced by the disease. This corresponds to the numerous exudates composed of differently constituted fibrinous materials, as also to the frequent impurity of blastemata in general.

The more important forms, described from the most perfect specimens, are as follows: -

1. Fibrin Taken From The Dead Bodies Of Healthy Individuals

Fibrin Taken From The Dead Bodies Of Healthy Individuals, presents tolerably compact and tough, moderately adhesive coagulations of a yellowish white. These are separable into membranous layers, and their torn surface exhibits a delicately villous character. Viewed under the microscope, they display a transparent basement, capable of membranous expansion, or else stratified. Upon this is a dense felt, freely erect at the edges of the preparation, and consisting of very minute, very elastic, ramified fibres, visible in black outline, and rapidly soluble in acetic acid. Hard by on the preparation, are seen numerous round polished nuclei, which, when treated with acetic acid, are brought more distinctly into relief. Beside these lie scattered minutely granular, dull, round, and elliptic nuclei, and similar cells, the size of pus-cells, colorless blood-globules, lymph-globules (fibrin-globules, according to Mandel), the same form-elements which, in exudates, are termed plastic corpuscles (Bennett) exudation cells (Henle). (See also Pappenheim, Addison, and others).

The soft, jelly-like coagula of so-called spurious fibrin, found to accompany the above-mentioned compact coagula, and in certain cases to constitute the whole of the impoverished fund of fibrin, show the same composition. They constitute, we think, a transition form from albumen to fibrin, of great moment in relation to the normal process of nutrition.

2. Fibrin The Coagula

Fibrin The Coagula of which, though of the ordinary appearance, possess the property of adhesiveness in a more marked degree, and frequently inclose not inconsiderable quantities of serum. Examined with the microscope, they present a laminated basement, and one splitting into fibres, flattened or roundish, rough, and firm, or resembling organic muscular fibres; or else a membranous basement invested with delicate wavy fibres, upon which, amongst elementary granules, are seen numerous round, black-edged nuclei, sometimes rod-shaped, or drawn out into fibres, and again, more especially in the moisture poured out, dull, round, and oval nuclei, and analogous cells. This fibrin enters - along with rudiments of the preceding one - into frequent combinations with those about to follow.

This and the preceding fibroid together furnish the basis of numerous areolar or fibrinous new growths, whether simple or combined with other blastemata, both within and without the vascular system; textural development having set in with the process of coagulation itself. The exudation of the last specified form of fibrin is especially wont to accompany morbid processes; for example, inflammation, and frequently in considerable abundance. It might be designated, for distinction's sake, as plastic or organizable fibrin.

3. Fibrin, The Coagula Of Which Are Marked By Opacity

Fibrin, The Coagula Of Which Are Marked By Opacity, and by a dull-white aspect shaded with yellowish, or with yellowish-green. They frequently include, besides blood-serum, blood-corpuscles in considerable amount, thus giving proof both of augmented coagulability, and greater rapidity of coagulation. They are opaque, and of various shades of red. Microscopically examined, the coagulum presents a stratiform or fibro-laminated basement, or else a faintly striated membrane, both being, however, opaque, owing to delicate granulation (Punktmasse). Upon this, as also in the serum, are seen a vast number of nucleus-like formations, of developed, dull granulated nuclei, and of similar more or less developed cells. Frequently the coagulum appears to consist altogether of the two last-mentioned elements, with a proportion of granulated structure. The nucleus-formations all manifest the usual neutral relations towards acetic acid. This fibrin possesses little adhesive property.

4. Fibrin Presenting In A Higher Degree The Morbid Characters

Fibrin Presenting In A Higher Degree The Morbid Characters manifested in the preceding variety. The coagula are extremely opaque, and, where they inclose no blood-corpuscles, of a more marked greenish-yellow tinge. Frequently, however, they do inclose vast quantities of blood-corpuscles, and are of a reddish-gray or a reddish-brown, denoting rapid coagulation. Upon a closer examination, they are found to consist of a compact, delicately granulated mass of nucleus and cell-formations (assimilating in various degrees to the pus-cell and pus-nucleus), all held together by a tough amorphous intercellular substance. There is neither fibrous tissue nor any fibrillation. These coagula possess still less of a cementing property.

These two latter forms we would designate as croupous fibrin. Here the fibrin borders upon that in pyaemia, and has the croupous character. The cells and nuclei included in the coagulum are genuine pus-nuclei and pus-cells. Other morbid conditions of fibrin - for example, the milky white opaque fibrin - are of little moment as regards the present subject. They will be considered under the head of Crases.

These forms of fibrin possess, from the very first, an indwelling prone-ness to textural formation, and a disposition to molecular disintegration - nay, they have already entered upon both the one and the other transformation. The fibrin 1 and 2, are organizable; the fibrin 3 and 4 suffer disintegration; portions of the fibrin 1 and 2 that mingle with it being alone susceptible of textural transformation, as is so frequently witnessed, extraneously to the vascular system, in exudations of a kindred stamp. Fibrin 4 presents no definite coagulum at all.

These forms of fibrin correspond in some measure with Mulder's gradations of the oxidation of protein. Here, however, chemical analysis has assuredly not kept pace with anatomical facts.

Coagula assuming as it were the form of intercellular substance, are liable to both kinds of metamorphosis. The differently apportioned nucleus and cell-formations here play a subordinate part, their importance varying, as has been stated, from the nucleus employed in the fabric of textures, to the true pus-nucleus and pus-cell. Hence they are the manifestation either of a quantitative endogenous development of textural rudiments, or else of a qualitative affection of the plasma.

1. The Structural Transformation

The Structural Transformation comprised in the process of coagulation, consists in the afore-mentioned diverse fibre-and membrane-formation. The nuclei themselves, sometimes appear elongated into rod- or perhaps spindle-shaped fibre-stems. In the cells the caudate form of development is seldom observable.

2. The Second Metamorphosis

The Second Metamorphosis is disintegration. It is foreshadowed in the granular mass that enters into the coagulation. After probably a brief interval, the entire coagulum resolves itself into a pulpy, creamlike, whitish, or yellowish-white, or, if containing blood-corpuscles, into a proportionally faint reddish-gray, reddish-brown, or chocolate-colored liquor, pregnant with granulated substance along with the nucleus and cell-formations originally admitted into the coagulation, and becoming, where the latter are numerous, relatively analogous to, and where they assume the character of pus-nuclei and pus-cells, identical with, pus. This breaking down may, under certain external conditions, unfavorable to textural formation, or owing to some indwelling peculiarity, affect fibrin generally. In croupous fibrin it is of unfailing occurrence. The results of Gulliver's experiments concerning the liquefaction of fibrinous coagula, under the sustained influence of the animal degree of heat, out of the animal body, are not applicable to the process as occurring within the living body, where certain kinds of fibrin of necessity become converted into textures, whilst others as invariably liquefy.

This process is witnessed with especial frequency in the coagula occurring within the heart, and which Laennec designated as vegetations globuleuses," as also in the coagula occurring within bloodvessels, both great and small.

Liquefied fibrin is capable of undergoing inspissation and cretaceous conversion.

Other Transformations Of Fibrin

Other Transformations Of Fibrin are:

3. The abiding of the organizable fibrin at the primitive stage of formation, and its eventual extinction. Here the coagulum is, with loss of its moisture, reduced to a compact, unyielding, semi-translucent, or opaque and horny substance. It is capable of eventually ossifying.

4. Fatty conversion, in the shape of a reduction to fat-molecules of various circumference, a metamorphosis which coagulate fibrin shares with liquid and coagulate albumen.

5. Within the vascular apparatus solidified albumen, of whatever form, may again become incorporated with the circulating fluid. Where this liquefaction of the coagulum is not the consequence of inherent disposition, it is wrought by gradual solution in the plasma, becoming, so to say, corroded, layer for layer, by the liquor sanguinis. Examples offer in the progressive resolution of solidified vegetations upon the heart's valves, or of the thrombus in arteries. It corresponds to the resorption of the consolidated fibrin of exudation and of extravasation.

We have hitherto expressly restricted ourselves to an inquiry concerning the consolidation and the metamorphoses of fibrin within the vascular apparatus, as exemplified in the diverse spontaneous coagulations which occur in the heart, not rarely during life; and again in coagulations within the larger vessels (more especially the veins), and also in the capillaries.

The relations of the fibrin of exudation are precisely the same. The organizable nature of the fibrin of exudation might be confidently assumed a priori; it is, however, as shown under the head of hemorrhage, directly demonstrable by facts.

Contrasting the frequency with which solid blastemata constitute the basis of pathological new growths, with their rareness in the physiological condition; reflecting, at the same time, upon the predominance of cell-development in physiological structures; and lastly, upon the absence of fibrin in the embryo, we feel somewhat disposed to concur with Zim-mermann, in regarding fibrin as a genuine excretive formation; a substance carried by oxidation to the verge of disintegration, - albumen worn out by oxidation, and associated with albumen for the purposes of nutrition, only in the shape of pseudo-fibrin.