When the exudation is abundant, as in the great lymph-sacs of the body—the several serous cavities—and especially when the openings in the walls of these sacs are obstructed or the currents within them are feeble, absorption takes place with great difficulty, and demands a long interval of time. The fibrinous and cellular portion of such an exudation frequently becomes converted into a caseous mass, from a partial fatty degeneration and inspissation. This mass becomes isolated from the cavity in which it lies, usually at the most dependent portion, by the formation of a capsule of connective tissue. It may subsequently become infiltrated with lime salts, calcified, and thus remain comparatively inert throughout the life of the individual.
The productive termination of inflammation is manifested by the new formation of connective tissue. This tissue is variously designated, as the inflammatory process is limited to the surfaces of the body exposed to the air, or the surfaces of cavities and organs, or as it lies within organs or the deep-seated parts of the body. In numerous instances it becomes a permanent constituent of the body, and, as time is usually essential for its formation, its occurrence is indicative of a chronic, rather than an acute inflammation. Certain chronic inflammations are progressive in character, the production of connective tissue being continuous, with perhaps occasional intermissions, as in the chronic interstitial inflammations of organs and tissues. The new-formed tissue, which at the outset is rich in cells, becomes in time more fibrous, and associated with this change in structure is a physical modification, manifested by its shrinkage. This new formation may fill a gap resulting from the destruction of tissue in the progress of an inflammation, when it is present as cicatricial tissue—the scar which is usually met with upon the surfaces of the body or of certain of its organs. When opposed surfaces are united by the new-formed tissue, the term adhesion is applied; the adhesions being present as fibrous bands, cords, or membranes. The pericardial milk-spots and thickenings, the tendinous or semi-cartilaginous, indurated patches of serous membranes and of the intima of arteries, are all regarded as manifestations of a chronic inflammation of these tissues. With the localization of the inflammation in the outer walls of the bronchi and blood-vessels a thickening of the external sheath results, called a peri-bronchitis, arteritis, or phlebitis, as the case may be.
The new formation of blood-vessels is essential for the production and preservation of this connective tissue, and both arise from pre-existing tissues. Pus-corpuscles represent the simple cellular product of an inflammation, and their existence is but transitory. With the new formation of blood-vessels imbedded in abundant cells there exists a granulation-tissue, likewise transitory, but out of which arises the permanent fibrous tissue. The question is still mooted as to the part played by exuded white blood-corpuscles in the production of the permanent results of inflammation. It is generally conceded, especially since the observations of Ziegler, that they are capable of transformation into lasting constituents of tissue, into blood-vessels as well as into cells and fibres. Whether all the resulting permanent products of inflammation are dependent upon their activity, or whether the pre-existing fixed elements participate, is still to be considered undecided.
What, at present, appears most probable is, that from exuded leucocytes there arise, in the course of several days, larger cells—epithelioid or endothelioid—which are eventually associated with still larger cells, more irregular in shape, and provided with projecting filaments, giant-cells. Both varieties may result from the enlargement of leucocytes by fusion or by the assimilation of nutriment. The epithelioid cells eventually become fusiform or stellate, and their projections, as well as those of many of the giant-cells, become fibrillated. The fibrils of adjoining cells, becoming united, are thus transformed into a meshwork of fibrous bundles enclosing irregular spaces, while the nuclei of the cells, with the immediately surrounding protoplasm, remain upon these bundles as the permanent cells of the new-formed tissue. The blood-vessels arise from pre-existing vessels, chiefly capillaries, and probably are also formed from the cells present in the exudation. The former method is indicated by the projection of solid sprouts from the wall of a capillary, which may unite, forming arches, and communicate with sprouts from neighboring capillaries, thus forming bridges. Both arches and bridges then become hollowed and admit the circulating blood. Ziegler maintains that the projections of the larger epithelioid cells and giant-cells become elongated, and eventually fused with capillaries, or the projections from capillaries. When this fusion is accomplished the cells become hollowed, their cavities communicating with those of the blood-vessels. These epithelioid cells, whose formation and transformation are of such importance in the history of productive inflammation, are designated by Ziegler as formative cells, and are frequently derived from the exuded white blood-corpuscles, though not identical with them.
The inflammations not terminating in resolution or production, end in the destruction of the part. This result occurs when the nutrition of the inflamed territory is so diminished, by the changes in and around the vessels, as to become insufficient for its preservation. As the nutriment is derived through the blood-vessels, the more complete and the more permanent the stagnation in them the more likely is death to result. This event also depends upon the quantity and quality of the exudation. The more abundantly cellular the latter, the more likely is an abscess or ulcer to result.
As most abundantly cellular exudations are considered to be dependent upon the presence of putrefactive agencies, those inflammations of a predominant putrid character (gangrenous inflammations) are those terminating in destruction. The dead product is present as a slough or sequestrum, when dead soft or hard tissues are detached, entire or in part, from the living; or as a granular detritus contained in a more or less abundant liquid. The inflammatory process producing the slough and sequestrum is characterized as a gangrenous inflammation of soft parts or a caries of bone, while the process resulting in the formation of the granular detritus, and which has no necessary connection with putrefactive agencies, is called a softening, from the physical condition of its result.
Thrombosis and Embolism.
A blood-clot formed within a blood-vessel during life is called a thrombus. The entire process of which the thrombus is the essential element is designated thrombosis.
These terms were introduced by Virchow17 to avoid the confusion which resulted from regarding the process and result as synonymous with inflammation of the vessel. All writers, even at present, do not adhere to this strictness of meaning. For a thrombus of the vulva indicates a clot of extravasated blood within the connective tissue of the labium; in like manner, a vaginal thrombus is the effused and clotted blood in the loose connective tissue surrounding the vagina. These exceptions are gradually disappearing, and the word hæmatoma, tumor composed of clotted blood, is being substituted in both instances. A cancerous thrombus represents a mass of cancerous tissue whose growth is extended along the course of a vessel, its wall having been penetrated. In general, however, the term thrombus, unless otherwise qualified, is used as first stated.
17 Handbuch der Speciellen Pathologie und Therapie, Erlangen, 1854, i. 159.