6. =Cartilaginous Tumors.= The _Enchondromata_, histologically resemble cartilage, and like it consist of cells and an intercellular substance, presenting all the variations observed in the normal tissue. The intercellular substance may be hyaline, fibrous, or mucoid, or as most frequently is the case, all combined. The cells are round, oval, spindle-shaped or stellate, and may be very numerous, or few in proportion to the matrix. They enclose one or more nuclei, and slightly granular contents; sometimes a cell-wall cannot be distinguished. In addition to the intercellular tissue, the growth is usually divided into several lobes by bands of fibrous tissue. The fibrous tissue in most cases, forms a capsule around the tumor, and separates it from the surrounding structures. The enchondroma is met with most frequently in early life, and occurs chiefly in connection with the osseous system, principally the metacarpal bones, and phalanges of the fingers, where it may grow either from the periosteum or from the medulla. It is met with also in the parotid and submaxillary glands, in the testicle, mammæ and ovary, and occasionally in the subcutaneous and intermuscular cellular tissue. They may attain an enormous size. “To the hand, it imparts the sensation of unusual firmness and solidity; it is destitute of elasticity, is generally distinctly circumscribed, and is nearly always strongly adherent to the tissues from which it springs.” Calcification and ossification of these tumors may occur. In rare cases, the skin covering the tumor ulcerates, and a fungating mass protrudes. Although in general an innocent growth, the enchondroma in some instances, assumes a malignant form, and recurs after extirpation. 7. =Osseous Tumors.= The _Osteomata_ are tumors consisting of osseous tissue, met with chiefly as outgrowths of the skeleton, especially of the external and internal surfaces of the skull, and of the thigh bone. There are three classes, the soft, spongy or cancellous, the compact, and the eburnated osteoma. The _spongy_, which is the most common, consists of cancellous osseous tissue. The medullary spaces may contain embryonic tissue, a fibrillated tissue, or fat. “In its earlier stages, it is often invested by a layer of cartilage, of a greenish, whitish, slightly bluish, or pearly aspect, and of a hyaline character. Sometimes it is enclosed by a thin, fibrous, or fibro-cellular capsule, a form of synovial bursa, lubricated by serous or sero-oleaginous fluid.” The _compact osteoma_ is generally more or less rounded, with a nodulated surface, and a broad base. It is of a firm, bony consistence, and resembles, as nearly as possible in structure, the compact tissue of the long bones, differing only in the arrangement of the Haversian canals and canaliculi, which is less regular than in normal bone.