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 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 haemolysis, which corresponds to the disintegration of other unsuccessful homoplastic grafts. (See article on Transfusion, Op.  Surg., p. 37.)