In what has gone before the phenomena described have been chiefly those of the earlier periods of inflammation and hence of the acute stage. Some inflammations, however, have no acute stage, and others after an acute period become less intense; in both cases changes ensue which result chiefly in new-formation of tissue. It may be said, indeed, that most Chronic inflammations are characterized by new-formation. Besides this, much depends on the nature of the irritant. There are some agents which affect chiefly the blood-vessels, others which involve mainly the parenchyma, whilst others produce their effects mainly on the connective tissues, and lead to new-formation as their principal characteristic. The new-formed tissue sometimes exercises an important function in serving as a bond of union between surfaces which have been separated, but it is very frequently of no such beneficial character. Thus both the tubercular and syphilitic infections are characterized by the formation of tissue, which in both cases shows commonly a degenerative tendency. The processes concerned in these and other similar diseases may be designated specific inflammations.

(a) The Granulating Wound, with its subsequent development into the Cicatrix, may be taken as a type of the inflammatory new-formation. On the infliction of a wound there are first the phenomena of acute inflammation with exudation of serous fluid and leucocytes such as have been already described. As the irritation of the actual infliction of the wound subsides, and provided the wound does not unite at once (first intention), a milder and more prolonged irritation usually ensues, caused in various ways by the friction of dressings, by decomposition of discharges, etc., with the result that so-called granulations cover the exposed surface. If the wound be carefully protected, by antiseptic precautions and otherwise, from all irritation, both mechanical and chemical, then the granulations do not form.

Granulations present to the naked eye a red, somewhat irregular, surface, and consist of a highly cellular and highly vascular tissue. There is here new-formation of cells and blood-vessels. The Cells of which the granulations are chiefly composed are of two kinds. (See Fig. 63.) There are first the ordinary leucocytes of the polymorphonuclear kind which have been derived from the vessels and form part of the exudation which granulations mostly yield. They are here merely in transit from the vessels to the surface or to the lymphatics. In addition to these there are larger cells with round or oval nuclei. These are the true tissue cells of the granulations and are concerned in the new-formation of tissue.

Soon after the infliction of a wound the fixed cells of the tissues, that is to say, the connective tissue and epidermic cells show the active nuclear changes of karyomitosis, and these changes are also visible in the walls of the blood-vessels. There is thus very early a new-formation of cells by division, and it is by this process that the granulations are by degrees produced. The cells, which by contrast with the leucocytes, are large, have some resemblance to epithelial cells, and are hence called Epithelioid cells. As they are concerned in the formation of the future permanent tissue they are also called, more appropriately, Formative cells. Besides these there are sometimes cells of a similar character, but of larger size and with several nuclei, the so-called Giant cells, which, however, are infrequent in granulations and are more characteristic of the specific inflammations.

The granulation tissue may be regarded as a kind of embryonic tissue, without the definite characters of any of the mature tissues of the body. Like embryonic tissue it has the power of developing mature tissue, but its powers are much more limited than those of the fœtal embryonic tissue. With the exception of the cells derived from epithelium at the edges of the wound it is connective tissue which the granulations are capable of forming. The granulation cells are mostly derived from connective tissue, and are inclined to pass back into the same kind of tissue. The first stage in this direction is an elongation of the cells, so that the more or less round epithelioid cells become spindle-shaped. In the deeper parts of the granulating wound there are frequently considerable layers of spindle-cell tissue. (See Fig. 64.) The next stage is the formation of the fibrous intercellular substance, which occurs by the production of a homogeneous or fibrillated material between the cells. This arises by a kind of secretion on the part of the cells, and the latter at the same time shrink greatly and form the small elongated connective-tissue corpuscles of the cicatrix. The Cicatrix is thus composed of new-formed connective tissue; but it is imperfectly formed, the intercellular substance being usually denser than that of ordinary connective tissue, and with a tendency to shrink which often lasts lorig after its first formation.

From superficial part of a granulating wound.

Fig. 63. - From superficial part of a granulating wound. Large formative cells and leucocytes are shown. ,

From deeper part of a granulating wound fepmdle shaped cells with occasional leucocytes are shown.

Fig. 64. - From deeper part of a granulating wound fepmdle-shaped cells with occasional leucocytes are shown.

The blood-vessels of the granulating wound form a rich system of capillaries, mostly in the form of loops passing towards the surface and returning. (See Fig. 65.) They form by a process of budding from the existing vessels of the part. The protoplasm of one of the cells in the wall of a small artery or capillary protrudes outward, like a bud, and extends to a neighbouring vessel, or to a corresponding process from another vessel. In this way solid arches (see Fig. 66) are formed which increase in thickness. The vessels are formed by the tunnelling of these. It has been asserted that the tunnelling takes place by the conversion of some of the protoplasm into red corpuscles in a manner similar to that which occurs in the original formation of vessels in the embryo, but this is very doubtful. According to Thiersch blood-vessels may be formed by a process of channelling among the cells. The wall of the vessel, infiltrated and softened by the inflammation, allows the blood plasma to pass out, and this forms canals which widen and admit the blood-corpuscles, but this is doubted by other authors, such as Arnold and Yamagiwa.

Vessels of a granulating wound injected.

Fig. 65. - Vessels of a granulating wound injected. (Billroth).

New formation of blood vessels in a granulating wound.

Fig. 66. - New-formation of blood-vessels in a granulating wound. (After Arnold).

Bone and cartilage are, histologically, forms of connective tissue, and they are, in pathological processes, to some extent interchangeable with ordinary connective tissue. Hence in inflammatory new-formations we may have, according to circumstances, these tissues produced along with or instead of connective tissue. This applies more particularly to inflammations in connection with bone. In fractures, for example, the so-called callus is composed, in many cases, of all three tissues.