soft variety grows much more rapidly than the hard.  In certain fibromas—­in those, for example, which grow from the periosteum of the base of the skull and project into the naso-pharynx—­the blood vessels are dilated into sinuses and have no proper sheaths; they therefore tend to remain open when divided, and to bleed excessively.  Transition forms between soft fibroma and sarcoma are met with, so that in operating for their removal it is safer to take away the capsule along with the tumour, and the patient should be kept under observation in view of the risk of recurrence.

The skin—­especially the skin of the buttock—­is one of the favourite seats of fibroma, and it may occur in a multiple form.  It is met with also in the subcutaneous and intermuscular cellular tissue, and in the abdominal wall, where it sometimes attains considerable dimensions.  Various forms of fibroma are met with in the mamma and are described with diseases of that organ.  The fibrous overgrowths in the skin, known as keloid and molluscum fibrosum, and those met with in the sheaths of nerves, are described elsewhere.  Fibroid tumours of the uterus are described with myoma.

Diffuse fibroma or Fibromatosis, analogous to lipomatosis, is met with in the connective tissue of the skin and sheaths of nerves, and constitutes one form of neuro-fibromatosis; a similar change is also met with in the stomach and colon.

#Myxoma.#—­A myxoma is composed of tissue of a soft gelatinous, semifluid consistence.  The pure myxoma is extremely rare, and clinically resembles the lipoma.  Myxomatous tissue is, however, frequently found in other connective-tissue tumours as a result of degeneration, for example, in cartilaginous tumours and in sarcomas.  Myxomatous tissue is also a prominent constituent of the “innocent parotid tumour.”  Mucous polypus of the nose, which is often described as a myxoma, is merely a pendulous process of oedematous mucous membrane.

[Illustration:  FIG. 53.—­Myeloma of Shaft of Humerus, causing pathological fracture. (Mr. J. W. Struthers’ case.)

(The unusual site of the tumour is to be noted.)]

#Myeloma.#—­A myeloma is composed of large multinuclear giant cells surrounded by round and spindle cells.  The cut surface of the tumour presents a deep red or maroon colour.  While occasionally met with in tendon sheaths and bursae, and is then of an orange-yellow colour, the myeloma occurs most frequently in the cancellous tissue at the ends of the long bones, its favourite site being the upper end of the tibia.  Although formerly classified as a sarcoma, it is the exception for it to present malignant features, and it can usually be extirpated by local measures without fear of recurrence.  The diagnosis, X-ray appearances, and the method of removal are considered with the diseases of bone.  Sometimes the myeloma is met with in multiple form in the skeleton, in association with an unusual form of protein in the urine (Bence Jones).