ntermediary stage in the healing of fractures, especially in young
bones. It may also take place in the regeneration of lost portions of
cartilage, provided the new tissue is so situated as to constitute part
of a joint and to be subjected to pressure by an opposing cartilaginous
surface. This is illustrated by what takes place after excision of
joints where it is desired to restore the function of the articulation.
By carrying out movements between the constituent parts, the fibrous
tissue covering the ends of the bones becomes moulded into shape, its
cells take on the characters of cartilage cells, and, forming a matrix,
so develop a new cartilage.

Conversely, it is observed that when articular cartilage is no longer
subjected to pressure by an opposing cartilage, it tends to be
transformed into fibrous tissue, as may be seen in deformities attended
with displacement of articular surfaces, such as hallux valgus and
club-foot.

After fractures of costal cartilage or of the cartilages of the larynx
the cicatricial tissue may be ultimately replaced by bone.

_Tendons._--When a tendon is divided, for example by subcutaneous
tenotomy, the end nearer the muscle fibres is drawn away from the other,
leaving a gap which is speedily filled by blood-clot. In the course of a
few days this clot becomes permeated by granulation tissue, the
fibroblasts of which are derived from the sheath of the tendon, the
surrounding connective tissue, and probably also from the divided ends
of the tendon itself. These fibroblasts ultimately develop into typical
tendon cells, and the fibres which they form constitute the new tendon
fibres. Under aseptic conditions repair is complete in from two to three
weeks. In the course of the reparative process the tendon and its sheath
may become adherent, which leads to impaired movement and stiffness. If
the ends of an accidentally divided tendon are at once brought into
accurate apposition and secured by sutures, they unite directly with a
minimum amount of scar tissue, and function is perfectly restored.

_Muscle._--Unstriped muscle does not seem to be capable of being
regenerated to any but a moderate degree. If the ends of a divided
striped muscle are at once brought into apposition by stitches, primary
union takes place with a minimum of intervening fibrous tissue. The
nuclei of the muscle fibres in close proximity to this young cicatricial
tissue proliferate, and a few new muscle fibres may be de