#--Innocent tumours, such as _lipoma_,
_fibroma_, and _myxoma_, are rare. Special mention should be made of the
_myeloma_ which is met with at the wrist or ankle as an elongated
swelling of slow development, or over the phalanx of a finger as a small
rounded swelling. The tumour tissue, when exposed by dissection, is of a
chocolate or chamois-yellow colour, and consists almost entirely of
giant cells. The treatment consists in dissecting the tumour tissue off
the tendons, and this is usually successful in bringing about a
permanent cure.

All varieties of _sarcoma_ are met with, but their origin from tendon
sheaths is not associated with special features.

CHAPTER XIX

THE BURSAE

Anatomy--Normal and adventitious bursae--Injuries: Bursal
haematoma--DISEASES: Infective bursitis; Traumatic or trade
bursitis; Bursal hydrops; Solid bursal tumour; Gonorrhoeal and
suppurative forms of bursitis; Tuberculous and syphilitic
disease--Tumours--_Diseases of individual bursae in the upper and
lower extremities_.

A bursa is a closed sac lined by endothelium and containing synovia.
Some are normally present--for instance, that between the skin and the
patella, and that between the aponeurosis of the gluteus maximus and the
great trochanter. _Adventitious bursae_ are developed as a result of
abnormal pressure--for example, over the tarsal bones in cases of
club-foot.

#Injuries of Bursae.#--As a result of contusion, especially in bleeders,
haemorrhage may occur into the cavity of a bursa and give rise to a
_bursal haematoma_. Such a haematoma may mask a fracture of the bone
beneath--for example, fracture of the olecranon.

#Diseases of Bursae.#--The lining membrane of bursae resembles that of
joints and tendon sheaths, and is liable to the same forms of disease.

#Infective bursitis# frequently follows abrasions, scratches, and wounds
of the skin over the prepatellar or olecranon bursa, and in neglected
cases the infection transgresses the wall of the bursa and gives rise to
a spreading cellulitis.

#Traumatic or Trade Bursitis.#--This term may be conveniently applied to
those affections of bursae which result from repeated slight traumatism
incident to particular occupations. The most familiar examples of these
are the enlargement of the prepatellar bursa met with in housemaids--the
"housemaid's knee" (Fig. 113); the enlargement of the olecranon
bursa--"miner's elbow"; and of the ischial bursa-