with which the graft is in contact: a portion of sterilised marine
sponge, for example, may be observed to become permeated with
granulation tissue when it is embedded in the tissues.

A successful graft of living tissue is not only capable of regeneration,
but it acquires a system of lymph and blood vessels, so that in time it
bleeds when cut into, and is permeated by new nerve fibres spreading in
from the periphery towards the centre.

It is instructive to associate the period of survival of the different
tissues of the body after death, with their capacity of being used for
grafting purposes; the higher tissues such as those of the central
nervous system and highly specialised glandular tissues like those of
the kidney lose their vitality quickly after death and are therefore
useless for grafting; connective tissues, on the other hand, such as
fat, cartilage, and bone retain their vitality for several hours after
death, so that when they are transplanted, they readily "take" and do
all that is required of them: the same is true of the skin and its
appendages.

_Sources of Grafts._--It is convenient to differentiate between
_autoplastic_ grafts, that is those derived from the same individual;
_homoplastic_ grafts, derived from another animal of the same species;
and _heteroplastic_ grafts, derived from an animal of another species.
Other conditions being equal, the prospects of success are greatest with
autoplastic grafts, and these are therefore preferred whenever possible.

There are certain details making for success that merit attention: the
graft must not be roughly handled or allowed to dry, or be subjected to
chemical irritation; it must be brought into accurate contact with the
new soil, no blood-clot intervening between the two, no movement of the
one upon the other should be possible and all infection must be
excluded; it will be observed that these are exactly the same conditions
that permit of the primary healing of wounds, with which of course the
healing of grafts is exactly comparable.

_Preservation of Tissues for Grafting._--It was at one time believed
that tissues might be taken from the operating theatre and kept in cold
storage until they were required. It is now agreed that tissues which
have been separated from the body for some time inevitably lose their
vitality, become incapable of regeneration, and are therefore unsuited
for grafting purposes. If it is intended to preserve a portion of