Under the microscope the first stage of perichondritis is marked by the appearance in the fibrous basis-substance of the perichondrium of more or less coarsely granular corpuscles, the so-called inflammatory corpuscles. As to their origin, it is well known that Virchow taught that they are produced by the enlargement, division, and subdivision of the connective-tissue corpuscles, while Cohnheim claimed that they are nothing but emigrated {120} colorless blood-corpuscles: in point of fact, most of them arise from the liberation of the living matter contained in the basis-substance, by the liquefaction or melting out of the non-living ingredient, and the increase and division of this matter into medullary or inflammatory corpuscles which constitute the so-called inflammatory infiltration. So long as the corpuscles remain connected by filaments of living matter, the inflammatory process may terminate by a new formation of basis-substance in hyperplasia--_i.e._ in the new formation of connective tissue. When, on the contrary, the inflammatory corpuscles are torn apart and become suspended in a liquid exudate, they constitute pus, and then the termination of the inflammatory process is in suppuration; that is to say, usually in an abscess. The perichondrium and cartilage are normally so closely connected that the one tissue passes gradually into the other without definite boundary-line, and the cartilage participates in the inflammatory process by a liquefaction of its basis-substance, reappearance of the living matter therein contained, and the formation of more inflammatory corpuscles. So long as the inflamed perichondrium remains in living connection with the cartilage, both tissues may participate in the new formation of a dense connective tissue, and hyperplasia be the result of the perichondritis and chondritis. Should, on account of suppuration at the boundary of the cartilage, the vascularized portion of the perichondrium become detached, the cartilage, being itself devoid of blood-vessels, will become dead. Its corpuscles will shrivel, and together with the lifeless basis-substance become disintegrated. Pieces of necrotic cartilage may be found lying in the surrounding pus, and, though usually chondritis has preceded the necrosis, the latter may ensue without previous change of the cartilage tissue, especially if the perichondritis runs its course to suppuration rapidly; but in every case suppurative perichondritis precedes necrosis of the cartilage. After the elimination of necrosed portions cartilage is as a rule replaced by newly-formed dense fibrous connective tissue. Some clinically-observed cases, aside from the remarkable case of Cohen already mentioned, indicate, however, that, exceptionally, new formation of cartilage may occur from hyperplastic perichondrium, in the same manner as new bone is sometimes formed from hyperplastic periosteum after osseous necrosis.