Open main menu

CHAPTER I

REPAIR


Introduction--Process of repair--Healing by primary union--Granulation

   tissue--Cicatricial tissue--Modifications of process of
   repair--Repair in individual tissues--Transplantation or grafting
   of tissues--Conditions--Sources of grafts--Grafting of individual
   tissues--Methods.


INTRODUCTION

To prolong human life and to alleviate suffering are the ultimate objects of scientific medicine. The two great branches of the healing art--Medicine and Surgery--are so intimately related that it is impossible to draw a hard-and-fast line between them, but for convenience Surgery may be defined as "the art of treating lesions and malformations of the human body by manual operations, mediate and immediate." To apply his art intelligently and successfully, it is essential that the surgeon should be conversant not only with the normal anatomy and physiology of the body and with the various pathological conditions to which it is liable, but also with the nature of the process by which repair of injured or diseased tissues is effected. Without this knowledge he is unable to recognise such deviations from the normal as result from mal-development, injury, or disease, or rationally to direct his efforts towards the correction or removal of these.


PROCESS OF REPAIR

The process of repair in living tissue depends upon an inherent power possessed by vital cells of reacting to the irritation caused by injury or disease. The cells of the damaged tissues, under the influence of this irritation, undergo certain proliferative changes, which are designed to restore the normal structure and configuration of the part. The process by which this restoration is effected is essentially the same in all tissues, but the extent to which different tissues can carry the recuperative process varies. Simple structures, such as skin, cartilage, bone, periosteum, and tendon, for example, have a high power of regeneration, and in them the reparative process may result in almost perfect restitution to the normal. More complex structures, on the other hand, such as secreting glands, muscle, and the tissues of the central nervous system, are but imperfectly restored, simple cicatricial connective tissue taking the place of what has been lost or destroyed. Any given tissue can be replaced only by tissue of a similar kind, and in a damaged part each element takes its share in the reparative process by producing new material which approximates more or less closely to the normal according to the recuperative capacity of the particular tissue. The normal process of repair may be interfered with by various extraneous agencies, the most important of which are infection by disease-producing micro-organisms, the presence of foreign substances, undue movement of the affected part, and improper applications and dressings. The effect of these agencies is to delay repair or to prevent the individual tissues carrying the process to the furthest degree of which they are capable.

In the management of wounds and other diseased conditions the main object of the surgeon is to promote the natural reparative process by preventing or eliminating any factor by which it may be disturbed.

  1. Healing by Primary Union.#--The most favourable conditions for the

progress of the reparative process are to be found in a clean-cut wound of the integument, which is uncomplicated by loss of tissue, by the presence of foreign substances, or by infection with disease-producing micro-organisms, and its edges are in contact. Such a wound in virtue of the absence of infection is said to be _aseptic_, and under these conditions healing takes place by what is called "primary union"--the "healing by first intention" of the older writers.

  1. Granulation Tissue.#--The essential and invariable medium of repair in

all structures is an elementary form of new tissue known as _granulation tissue_, which is produced in the damaged area in response to the irritation caused by injury or disease. The vital reaction induced by such irritation results in dilatation of the vessels of the part, emigration of leucocytes, transudation of lymph, and certain proliferative changes in the fixed tissue cells. These changes are common to the processes of inflammation and 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 phagocytes. Numerous _polymorpho-nuclear leucocytes_, which have wandered from the vessels, are also present in the spaces. These act as phagocytes, their function being to remove the red corpuscles and fibrin of the original clot, and this performed, they either pass back into the circulation in virtue of their amoeboid movement, or are themselves eaten up by the growing fibroblasts. Beyond this phagocytic action, they do not appear to play any direct part in the reparative process. These young capillary loops, with their supporting cells and fluids, constitute granulation tissue, which is usually fully formed in from three to five days, after which it begins to be replaced by cicatricial or scar tissue.

_Formation of Cicatricial Tissue._--The transformation of this temporary granulation tissue into scar tissue is effected by the fibroblasts, which become elongated and spindle-shaped, and produce in and around them a fine fibrillated material which gradually increases in quantity till it replaces the cell protoplasm. In this way white fibrous tissue is formed, the cells of which are arranged in parallel lines and eventually become grouped in bundles, constituting fully formed white fibrous tissue. In its growth it gradually obliterates the capillaries, until at the end of two, three, or four weeks both vessels and cells have almost entirely disappeared, and the original wound is occupied by cicatricial tissue. In course of time this tissue becomes consolidated, and the cicatrix undergoes a certain amount of contraction--_cicatricial contraction_.

_Healing of Epidermis._--While these changes are taking place in the deeper parts of the wound, the surface is being covered over by _epidermis_ growing in from the margins. Within twelve hours the cells of the rete Malpighii close to the cut edge begin to sprout on to the surface of the wound, and by their proliferation gradually cover the granulations with a thin pink pellicle. As the epithelium increases in thickness it assumes a bluish hue and eventually the cells become cornified and the epithelium assumes a greyish-white colour.

_Clinical Aspects._--So long as the process of repair is not complicated by infection with micro-organisms, there is no interference with the general health of the patient. The temperature remains normal; the circulatory, gastro-intestinal, nervous, and other functions are undisturbed; locally, the part is cool, of natural colour and free from pain.

  1. Modifications of the Process of Repair.#--The process of repair by

primary union, above described, is to be looked upon as the type of all reparative processes, such modifications as are met with depending merely upon incidental differences in the conditions present, such as loss of tissue, infection by micro-organisms, etc.

_Repair after Loss or Destruction of Tissue._--When the edges of a wound cannot be approximated either because tissue has been lost, for example in excising a tumour or because a drainage tube or gauze packing has been necessary, a greater amount of granulation tissue is required to fill the gap, but the process is essentially the same as in the ideal method of repair.

The raw surface is first covered by a layer of coagulated blood and fibrin. An extensive new formation of capillary loops and fibroblasts takes place towards the free surface, and goes on until the gap is filled by a fine velvet-like mass of granulation tissue. This granulation tissue is gradually replaced by young cicatricial tissue, and the surface is covered by the ingrowth of epithelium from the edges.

This modification of the reparative process can be best studied clinically in a recent wound which has been packed with gauze. When the plug is introduced, the walls of the cavity consist of raw tissue with numerous oozing blood vessels. On removing the packing on the fifth or sixth day, the surface is found to be covered with minute, red, papillary granulations, which are beginning to fill up the cavity. At the edges the epithelium has proliferated and is covering over the newly formed granulation tissue. As lymph and leucocytes escape from the exposed surface there is a certain amount of serous or sero-purulent discharge. On examining the wound at intervals of a few days, it is found that the granulation tissue gradually increases in amount till the gap is completely filled up, and that coincidently the epithelium spreads in and covers over its surface. In course of time the epithelium thickens, and as the granulation tissue is slowly replaced by young cicatricial tissue, which has a peculiar tendency to contract and so to obliterate the blood vessels in it, the scar that is left becomes smooth, pale, and depressed. This method of healing is sometimes spoken of as "healing by granulation"--although, as we have seen, it is by granulation that all repair takes place.

_Healing by Union of two Granulating Surfaces._--In gaping wounds union is sometimes obtained by bringing the two surfaces into apposition after each has become covered with healthy granulations. The exudate on the surfaces causes them to adhere, capillary loops pass from one to the other, and their final fusion takes place by the further development of granulation and cicatricial tissue.

_Reunion of Parts entirely Separated from the Body._--Small portions of tissue, such as the end of a finger, the tip of the nose or a portion of the external ear, accidentally separated from the body, if accurately replaced and fixed in position, occasionally adhere by primary union.

In the course of operations also, portions of skin, fascia, or bone, or even a complete joint may be transplanted, and unite by primary union.

_Healing under a Scab._--When a small superficial wound is exposed to the air, the blood and serum exuded on its surface may dry and form a hard crust or _scab_, which serves to protect the surface from external irritation in the same way as would a dry pad of sterilised gauze. Under this scab the formation of granulation tissue, its transformation into cicatricial tissue, and the growth of epithelium on the surface, go on until in the course of time the crust separates, leaving a scar.

_Healing by Blood-clot._--In subcutaneous wounds, for example tenotomy, in amputation wounds, and in wounds made in excising tumours or in operating upon bones, the space left between the divided tissues becomes filled with blood-clot, which acts as a temporary scaffolding in which granulation tissue is built up. Capillary loops grow into the coagulum, and migrated leucocytes from the adjacent blood vessels destroy the red corpuscles, and are in turn disposed of by the developing fibroblasts, which by their growth and proliferation fill up the gap with young connective tissue. It will be evident that this process only differs from healing by primary union in the _amount_ of blood-clot that is present.

_Presence of a Foreign Body._--When an aseptic foreign body is present in the tissues, _e.g._ a piece of unabsorbable chromicised catgut, the healing process may be modified. After primary union has taken place the scar may broaden, become raised above the surface, and assume a bluish-brown colour; the epidermis gradually thins and gives way, revealing the softened portion of catgut, which can be pulled out in pieces, after which the wound rapidly heals and resumes a normal appearance.


REPAIR IN INDIVIDUAL TISSUES

_Skin and Connective Tissue._--The mode of regeneration of these tissues under aseptic conditions has already been described as the type of ideal repair. In highly vascular parts, such as the face, the reparative process goes on with great rapidity, and even extensive wounds may be firmly united in from three to five days. Where the anastomosis is less free the process is more prolonged. The more highly organised elements of the skin, such as the hair follicles, the sweat and sebaceous glands, are imperfectly reproduced; hence the scar remains smooth, dry, and hairless.

_Epithelium._--Epithelium is only reproduced from pre-existing epithelium, and, as a rule, from one of a similar type, although metaplastic transformation of cells of one kind of epithelium into another kind can take place. Thus a granulating surface may be covered entirely by the ingrowing of the cutaneous epithelium from the margins; or islets, originating in surviving cells of sebaceous glands or sweat glands, or of hair follicles, may spring up in the centre of the raw area. Such islets may also be due to the accidental transference of loose epithelial cells from the edges. Even the fluid from a blister, in virtue of the isolated cells of the rete Malpighii which it contains, is capable of starting epithelial growth on a granulating surface. Hairs and nails may be completely regenerated if a sufficient amount of the hair follicles or of the nail matrix has escaped destruction. The epithelium of a mucous membrane is regenerated in the same way as that on a cutaneous surface.

Epithelial cells have the power of living for some time after being separated from their normal surroundings, and of growing again when once more placed in favourable circumstances. On this fact the practice of skin grafting is based (p. 11).

_Cartilage._--When an articular cartilage is divided by incision or by being implicated in a fracture involving the articular end of a bone, it is repaired by ordinary cicatricial fibrous tissue derived from the proliferating cells of the perichondrium. Cartilage being a non-vascular tissue, the reparative process goes on slowly, and it may be many weeks before it is complete.

It is possible for a metaplastic transformation of connective-tissue cells into cartilage cells to take place, the characteristic hyaline matrix being secreted by the new cells. This is sometimes observed as an intermediary 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 developed, but any gross loss of muscular tissue is replaced by a fibrous cicatrix. It would appear that portions of muscle transplanted from animals to fill up gaps in human muscle are similarly replaced by fibrous tissue. When a muscle is paralysed from loss of its nerve supply and undergoes complete degeneration, it is not capable of being regenerated, even should the integrity of the nerve be restored, and so its function is permanently lost.

_Secretory Glands._--The regeneration of secretory glands is usually incomplete, cicatricial tissue taking the place of the glandular substance which has been destroyed. In wounds of the liver, for example, the gap is filled by fibrous tissue, but towards the periphery of the wound the liver cells proliferate and a certain amount of regeneration takes place. In the kidney also, repair mainly takes place by cicatricial tissue, and although a few collecting tubules may be reformed, no regeneration of secreting tissue takes place. After the operation of decapsulation of the kidney a new capsule is formed, and during the process young blood vessels permeate the superficial parts of the kidney and temporarily increase its blood supply, but in the consolidation of the new fibrous tissue these vessels are ultimately obliterated. This does not prove that the operation is useless, as the temporary improvement of the circulation in the kidney may serve to tide the patient over a critical period of renal insufficiency.

_Stomach and Intestine._--Provided the peritoneal surfaces are accurately apposed, wounds of the stomach and intestine heal with great rapidity. Within a few hours the peritoneal surfaces are glued together by a thin layer of fibrin and leucocytes, which is speedily organised and replaced by fibrous tissue. Fibrous tissue takes the place of the muscular elements, which are not regenerated. The mucous lining is restored by ingrowth from the margins, and there is evidence that some of the secreting glands may be reproduced.

Hollow viscera, like the oesophagus and urinary bladder, in so far as they are not covered by peritoneum, heal less rapidly.

_Nerve Tissues._--There is no trustworthy evidence that regeneration of the tissues of the brain or spinal cord in man ever takes place. Any loss of substance is replaced by cicatricial tissue.

The repair of _Bone_, _Blood Vessels_, and _Peripheral Nerves_ is more conveniently considered in the chapters dealing with these structures.

  1. Rate of Healing.#--While the rate at which wounds heal is remarkably

constant there are certain factors that influence it in one direction or the other. Healing is more rapid when the edges are in contact, when there is a minimum amount of blood-clot between them, when the patient is in normal health and the vitality of the tissues has not been impaired. Wounds heal slightly more quickly in the young than in the old, although the difference is so small that it can only be demonstrated by the most careful observations.

Certain tissues take longer to heal than others: for example, a fracture of one of the larger long bones takes about six weeks to unite, and divided nerve trunks take much longer--about a year.

Wounds of certain parts of the body heal more quickly than others: those of the scalp, face, and neck, for example, heal more quickly than those over the buttock or sacrum, probably because of their greater vascularity.

The extent of the wound influences the rate of healing; it is only natural that a long and deep wound should take longer to heal than a short and superficial one, because there is so much more work to be done in the conversion of blood-clot into granulation tissue, and this again into scar tissue that will be strong enough to stand the strain on the edges of the wound.


THE TRANSPLANTATION OR GRAFTING OF TISSUES

Conditions are not infrequently met with in which healing is promoted and restoration of function made possible by the transference of a portion of tissue from one part of the body to another; the tissue transferred is known as the _graft_ or the _transplant_. The simplest example of grafting is the transplantation of skin.

In order that the graft may survive and have a favourable chance of "taking," as it is called, the transplanted tissue must retain its vitality until it has formed an organic connection with the tissue in which it is placed, so that it may derive the necessary nourishment from its new bed. When these conditions are fulfilled the tissues of the graft continue to proliferate, producing new tissue elements to replace those that are lost and making it possible for the graft to become incorporated with the tissue with which it is in contact.

Dead tissue, on the other hand, can do neither of these things; it is only capable of acting as a model, or, at the most, as a scaffolding for such mobile tissue elements as may be derived from, the parent tissue 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 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

  1. 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.)

  1. 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.

Skin grafts may be applied to a raw surface or to one that is covered with granulations.

_Skin grafting of raw surfaces_ is commonly indicated after operations for malignant disease in which considerable areas of skin must be sacrificed, and after accidents, such as avulsion of the scalp by machinery.

_Skin grafting of granulating surfaces_ is chiefly employed to promote healing in the large defects of skin caused by severe burns; the grafting is carried out when the surface is covered by a uniform layer of healthy granulations and before the inevitable contraction of scar tissue makes itself manifest. Before applying the grafts it is usual to scrape away the granulations until the young fibrous tissue underneath is exposed, but, if the granulations are healthy and can be rendered aseptic, the grafts may be placed on them directly.

If it is decided to scrape away the granulations, the oozing must be arrested by pressure with a pad of gauze, a sheet of dental rubber or green protective is placed next the raw surface to prevent the gauze adhering and starting the bleeding afresh when it is removed.

  1. Methods of Skin-Grafting.#--Two methods are employed: one in which the

epidermis is mainly or exclusively employed--epidermis or epithelial grafting; the other, in which the graft consists of the whole thickness of the true skin--cutis-grafting.

_Epidermis or Epithelial Grafting._--The method introduced by the late Professor Thiersch of Leipsic is that almost universally practised. It consists in transplanting strips of epidermis shaved from the surface of the skin, the razor passing through the tips of the papillae, which appear as tiny red points yielding a moderate ooze of blood.

The strips are obtained from the front and lateral aspects of the thigh or upper arm, the skin in those regions being pliable and comparatively free from hairs.

They are cut with a sharp hollow-ground razor or with Thiersch's grafting knife, the blade of which is rinsed in alcohol and kept moistened with warm saline solution. The cutting is made easier if the skin is well stretched and kept flat and perfectly steady, the operator's left hand exerting traction on the skin behind, the hands of the assistant on the skin in front, one above and the other below the seat of operation. To ensure uniform strips being cut, the razor is kept parallel with the surface and used with a short, rapid, sawing movement, so that, with a little practice, grafts six or eight inches long by one or two inches broad can readily be cut. The patient is given a general anaesthetic, or regional anaesthesia is obtained by injections of a solution of one per cent. novocain into the line of the lateral and middle cutaneous nerves; the disinfection of the skin is carried out on the usual lines, any chemical agent being finally got rid of, however, by means of alcohol followed by saline solution.

The strips of epidermis wrinkle up on the knife and are directly transferred to the surface, for which they should be made to form a complete carpet, slightly overlapping the edges of the area and of one another; some blunt instrument is used to straighten out the strips, which are then subjected to firm pressure with a pad of gauze to express blood and air-bells and to ensure accurate contact, for this must be as close as that between a postage stamp and the paper to which it is affixed.

As a dressing for the grafted area and of that also from which the grafts have been taken, gauze soaked in _liquid paraffin_--the patent variety known as _ambrine_ is excellent--appears to be the best; the gauze should be moistened every other day or so with fresh paraffin, so that, at the end of a week, when the grafts should have united, the gauze can be removed without risk of detaching them. _Dental wax_ is another useful type of dressing; as is also _picric acid_ solution. Over the gauze, there is applied a thick layer of cotton wool, and the whole dressing is kept in place by a firmly applied bandage, and in the case of the limbs some form of splint should be added to prevent movement.

A dressing may be dispensed with altogether, the grafts being protected by a wire cage such as is used after vaccination, but they tend to dry up and come to resemble a scab.

When the grafts have healed, it is well to protect them from injury and to prevent them drying up and cracking by the liberal application of lanoline or vaseline.

The new skin is at first insensitive and is fixed to the underlying connective tissue or bone, but in course of time (from six weeks onwards) sensation returns and the formation of elastic tissue beneath renders the skin pliant and movable so that it can be pinched up between the finger and thumb.

_Reverdin's_ method consists in planting out pieces of skin not bigger than a pin-head over a granulating surface. It is seldom employed.

_Grafts of the Cutis Vera._--Grafts consisting of the entire thickness of the true skin were specially advocated by Wolff and are often associated with his name. They should be cut oval or spindle-shaped, to facilitate the approximation of the edges of the resulting wound. The graft should be cut to the exact size of the surface it is to cover; Gillies believes that tension of the graft favours its taking. These grafts may be placed either on a fresh raw surface or on healthy granulations. It is sometimes an advantage to stitch them in position, especially on the face. The dressing and the after-treatment are the same as in epidermis grafting.

There is a degree of uncertainty about the graft retaining its vitality long enough to permit of its deriving the necessary nourishment from its new surroundings; in a certain number of cases the flap dies and is thrown off as a slough--moist or dry according to the presence or absence of septic infection.

The technique for cutis-grafting must be without a flaw, and the asepsis absolute; there must not only be a complete absence of movement, but there must be no traction on the flap that will endanger its blood supply.

Owing to the uncertainty in the results of cutis-grafting the _two-stage_ or _indirect method_ has been introduced, and its almost uniform success has led to its sphere of application being widely extended. The flap is raised as in the direct method but is left attached at one of its margins for a period ranging from 14 to 21 days until its blood supply from its new bed is assured; the detachment is then made complete. The blood supply of the proposed flap may influence its selection and the way in which it is fashioned; for example, a flap cut from the side of the head to fill a defect in the cheek, having in its margin of attachment or pedicle the superficial temporal artery, is more likely to take than a flap cut with its base above.

Another modification is to raise the flap but leave it connected at both ends like the piers of a bridge; this method is well suited to defects of skin on the dorsum of the fingers, hand and forearm, the bridge of skin is raised from the abdominal wall and the hand is passed beneath it and securely fixed in position; after an interval of 14 to 21 days, when the flap is assured of its blood supply, the piers of the bridge are divided (Fig. 1). With undermining it is usually easy to bring the edges of the gap in the abdominal wall together, even in children; the skin flap on the dorsum of the hand appears rather thick and prominent--almost like the pad of a boxing-glove--for some time, but the restoration of function in the capacity to flex the fingers is gratifying in the extreme.

[Illustration: FIG. 1.--Ulcer of back of Hand covered by flap of skin raised from anterior abdominal wall. The lateral edges of the flap are divided after the graft has adhered.]

The indirect element of this method of skin-grafting may be carried still further by transferring the flap of skin first to one part of the body and then, after it has taken, transferring it to a third part. Gillies has especially developed this method in the remedying of deformities of the face caused by gunshot wounds and by petrol burns in air-men. A rectangular flap of skin is marked out in the neck and chest, the lateral margins of the flap are raised sufficiently to enable them to be brought together so as to form a tube of skin: after the circulation has been restored, the lower end of the tube is detached and is brought up to the lip or cheek, or eyelid, where it is wanted; when this end has derived its new blood supply, the other end is detached from the neck and brought up to where it is wanted. In this way, skin from the chest may be brought up to form a new forehead and eyelids.

Grafts of _mucous membrane_ are used to cover defects in the lip, cheek, and conjunctiva. The technique is similar to that employed in skin-grafting; the sources of mucous membrane are limited and the element of septic infection cannot always be excluded.

_Fat._--Adipose tissue has a low vitality, but it is easily retained and it readily lends itself to transplantation. Portions of fat are often obtainable at operations--from the omentum, for example, otherwise the subcutaneous fat of the buttock is the most accessible; it may be employed to fill up cavities of all kinds in order to obtain more rapid and sounder healing and also to remedy deformity, as in filling up a depression in the cheek or forehead. It is ultimately converted into ordinary connective tissue _pari passu_ with the absorption of the fat.

The _fascia lata of the thigh_ is widely and successfully used as a graft to fill defects in the dura mater, and interposed between the bones of a joint--if the articular cartilage has been destroyed--to prevent the occurrence of ankylosis.

The _peritoneum_ of hydrocele and hernial sacs and of the omentum readily lends itself to transplantation.

_Cartilage and bone_, next to skin, are the tissues most frequently employed for grafting purposes; their sphere of action is so extensive and includes so much of technical detail in their employment, that they will be considered later with the surgery of the bones and joints and with the methods of re-forming the nose.

_Tendons and blood vessels_ readily lend themselves to transplantation and will also be referred to later.

_Muscle and nerve_, on the other hand, do not retain their vitality when severed from their surroundings and do not functionate as grafts except for their connective-tissue elements, which it goes without saying are more readily obtainable from other sources.

Portions of the _ovary_ and of the _thyreoid_ have been successfully transplanted into the subcutaneous cellular tissue of the abdominal wall by Tuffier and others. In these new surroundings, the ovary or thyreoid is vascularised and has been shown to functionate, but there is not sufficient regeneration of the essential tissue elements to "carry on"; the secreting tissue is gradually replaced by connective tissue and the special function comes to an end. Even such temporary function may, however, tide a patient over a difficult period.