a. (Cf. Fig. 114.)]

An adventitious bursa may form over the _lateral malleolus_, especially
in tailors, giving rise to the condition known as "tailor's ankle"
(Fig. 117).

The bursa _between the tendo-calcaneus (Achillis) and the upper part of
the calcaneus_ may become inflamed--especially as a result of
post-scarlatinal rheumatism or gonorrhoea. The affection is known as
Achillo-bursitis. There is severe pain in the region of the insertion of
the tendo-calcaneus, the movements at the ankle-joint are restricted,
and the patient may be unable to walk. There is a tender swelling on
either side of the tendon. When, in spite of palliative treatment, the
affection persists or relapses, it is best to excise the bursa. The
tendo-calcaneus is detached from the calcaneus, the bursa dissected out,
and the tendon replaced. If there is a bony projection from the
calcaneus, it should be shaved off with the chisel.

The bursa that is sometimes met with on the under aspect of the
calcaneus--_the subcalcanean bursa_--when inflamed, gives rise to pain
and tenderness in the sole of the foot. This affection may be associated
with a spinous projection from the bone, which is capable of being
recognised in a skiagram. The soft parts of the heel are turned forwards
as a flap, the bursa is dissected out, and the projection of bone, if
present, is removed.

The enlargement of adventitious bursae over the head of the first
metatarsal in hallux valgus; over the tarsus, metatarsus, and digits in
the different forms of club-foot; over the angular projection in Pott's
disease of the spine; over the end of the bone in amputation stumps, and
over hard tumours such as chondroma and osteoma, are described
elsewhere.

CHAPTER XX

DISEASES OF BONE

Anatomy and physiology--Regeneration of bone--Transplantation of bone.
DISEASES OF BONE--Definition of terms--Pyogenic diseases:
_Acute osteomyelitis and periostitis_; _Chronic and relapsing
osteomyelitis_; _Abscess of bone_--Tuberculous disease--Syphilitic
disease--Hydatids; Rickets; Osteomalacia--Ostitis deformans of
Paget--Osteomyelitis fibrosa--Affections of bones in diseases of
the nervous system--Fragilitas ossium--Tumours and cysts of bone.

#Surgical Anatomy.#--During the period of growth, a long bone such as
the tibia consists of a shaft or _diaphysis_, and two extremities or
_epiphyses_. So long as growth continues there intervenes between the
shaft and eac