These, as already stated, represent benign new growths. They are always purely local affections, and therefore exist almost always as a solitary growth. They are most commonly due to mechanical influences; accordingly their seat is generally in organs or parts near the surface, and obnoxious to such influences. They are curable by complete extirpation; that is they do not recur at the same spot, and still less do they multiply in other localities.

They generally constitute circumscribed, spherical, stellate, and clavate, superficially lobulated tumors. Often enough they ramify throughout the texture, nestling and luxuriating through the elementary parts, so that these perish, degenerating, so to say, into the heterologous growth.

They often increase to a very considerable volume, and this within a brief period.

They affect the areolar tissue, the fibrous membranes, - especially the submucous, - the muscles, inter-muscular tissue, and submucous muscular textures (uterus), the bones (osteo-sarcoma), particularly the facial bones, glandular organs, the mammary, the parotid glands, even the testicle; and, in rare instances, the brain.

The osteo-sarcoma is often inclosed within a skeleton sheath formed by the distended bone, which eventually becomes perforated. In rare instances a new growth of bone enters, in the shape of an inner skeleton or framework, into its composition.

Generally speaking, sarcomata are more frequent than carcinomata in the early periods of life - those of childhood and of boyhood.

They seldom lapse into a process of ichorous ulceration spontaneously, although frequently through inflammation brought on by the membranous expansions which covered them, namely, the general integument or the mucous membrane, inflaming and sloughing away, so as to leave them denuded. This ichorous ulceration may even lead to cachexia and exhaustion; the inflammation itself, however, never gives rise to a specific infection, and to a multiplied production of the heterologous growth.

Sarcomata lend themselves naturally to a division into three species.