repair; no hard-and-fast
line can be drawn between these processes, and the two may go on
together. It is, however, only when the proliferative changes have come
to predominate that the reparative process is effectively established by
the production of healthy granulation tissue.

_Formation of Granulation Tissue._--When a wound is made in the
integument under aseptic conditions, the passage of the knife through
the tissues is immediately followed by an oozing of blood, which soon
coagulates on the cut surfaces. In each of the divided vessels a clot
forms, and extends as far as the nearest collateral branch; and on the
surface of the wound there is a microscopic layer of bruised and
devitalised tissue. If the wound is closed, the narrow space between its
edges is occupied by blood-clot, which consists of red and white
corpuscles mixed with a quantity of fibrin, and this forms a temporary
uniting medium between the divided surfaces. During the first twelve
hours, the minute vessels in the vicinity of the wound dilate, and from
them lymph exudes and leucocytes migrate into the tissues. In from
twenty-four to thirty-six hours, the capillaries of the part adjacent to
the wound begin to throw out minute buds and fine processes, which
bridge the gap and form a firmer, but still temporary, connection
between the two sides. Each bud begins in the wall of the capillary as a
small accumulation of granular protoplasm, which gradually elongates
into a filament containing a nucleus. This filament either joins with a
neighbouring capillary or with a similar filament, and in time these
become hollow and are filled with blood from the vessels that gave them
origin. In this way a series of young _capillary loops_ is formed.

The spaces between these loops are filled by cells of various kinds, the
most important being the _fibroblasts_, which are destined to form
cicatricial fibrous tissue. These fibroblasts are large irregular
nucleated cells derived mainly from the proliferation of the fixed
connective-tissue cells of the part, and to a less extent from the
lymphocytes and other mononuclear cells which have migrated from the
vessels. Among the fibroblasts, larger multi-nucleated cells--_giant
cells_--are sometimes found, particularly when resistant substances,
such as silk ligatures or fragments of bone, are embedded in the
tissues, and their function seems to be to soften such substances
preliminary to their being removed by the pha