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 tissue
for future grafting, it should be embedded in the subcutaneous tissue of
the abdominal wall until it is wanted; this has been carried out with
portions of costal cartilage and of bone.


INDIVIDUAL TISSUES AS GRAFTS

#The Blood# lends itself in an ideal manner to transplantation, or, as
it has long been called, _transfusion_. Being always a homoplastic
transfer, the new blood is not always tolerated by the old, in which
case biochemical changes occur, resulting in hæmolysis, which
corresponds to the disintegration of other unsuccessful homoplastic
grafts. (See article on Transfusion, _Op. Surg._, p. 37.)

#The Skin.#--The skin was the first tissue to be used for grafting
purposes, and it is still employed with greater frequency than any
other, as lesions causing defects of skin are extremely common and
without the aid of grafts are tedious in healing.