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thumb is specially liable to spread upwards into the palm, and thence underneath the transverse carpal ligament into the forearm.

The pulsations of the radial artery can readily be felt in the distal third of the forearm, midway between the lateral border of the radius and the tendon of the flexor carpi radialis. The course of the vessel is indicated upon the surface by a line extending from the bifurcation of the brachial (in. distal to the middle of the bend of the elbow) to the tubercle of the navicular, around which, and distal to the tip of the styloid process, the artery winds to the dorsum of the radial side of the wrist; in the latter situation the vessel, after passing deep to the extensor tendons of the thumb, dips into the palm through the proximal extremity of the first interosseous space. Incisions for opening or resecting the wrist are planned so as to avoid the vessel.

The proximal third of the ulnar artery is deeply placed, and takes a curved course from the bifurcation of the brachial towards the medial part of the volar surface of the forearm; the distal two-thirds of the vessel correspond to the distal two-thirds of a line drawn from the front of the medial epicondyle to the radial border of the pisiform bone. The course of the ulnar nerve corresponds to the whole of the above line.

The median nerve in the forearm may be mapped out by a line extending from a point midway between the centre of the bend of the elbow and the medial epicondyle, to a point midway between the styloid processes; in the distal third of the forearm the line follows the medial border of the tendon of the flexor carpi radialis. To evacuate pus spreading deeply up the front of the forearm, the incisions should be made on either side of the line corresponding to the median nerve. The superficial branch of the radial nerve winds to the dorsum of the forearm round the lateral border of the radius deep to the tendon of the brachioradialis, at the junction of the middle and distal thirds of the forearm.

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The summit, or most distal part of the superficial palmar arch, corresponds to the mid-point of a line extending from the middle of the most distal transverse crease of the wrist to the root of the middle finger; a line drawn from the radial border of the pisiform bone across the hamulus of the os hamatum, and thence in a curved direction distally and laterally to this point, corresponds to the main or proximal part of the arch; the first and fourth digital branches overlie the fifth and third metacarpal bones respectively, while the second and third overlie the fourth and third interspaces respectively. The deep arch lies almost transversely, midway between the distal border of the transverse carpal ligament and the superficial arch. The radialis indicis corresponds to the radial border of the index-finger.

The ulnar nerve and the commencement of its two divisions lie immediately to the medial side of the superficial palmar arch, so that the pisiform and the hamulus of the os hamatum are the guides to the nerve. The median nerve emerges from under the transverse carpal ligament opposite the medial edge of the thenar eminence, while the digital branches to the thumb follow its distal margin. Incisions for the removal of foreign bodies may therefore be made into the thenar with greater freedom than into the hypo-thenar eminence.

Incisions to evacuate deep-seated pus in the palm may be made in one or more of the following situations: (1) over the distal two-thirds of the second metacarpal bone; (2) over the distal half of the fourth metacarpal bone; (3) from the proximal part of the first incision an opening may be made through the first interosseous space on to the dorsum. care being taken to keep distal to the radial artery; (4) a longitudinal incision between the median and ulnar nerves, on the proximal side of the superficial palmar arch. At the wrist a longitudinal incision may be made immediately to the ulnar side of the palmars longus tendon, thus falling between the lines of the median nerve and the ulnar artery To open the digital flexor sheaths, incisions are made along the middle of the palmar surface of the fingers, opposite the first and second phalanges. The proper digital vessels and nerves pass distally along the sides of the fingers, nearer the flexor than the extensor surfaces. In cutting down upon the dorsal aspects of the phalanges, the incisions should be made to one or other side of the extensor tendon, preferably upon the ulnar side, to avoid division of the insertions of lumbrical muscles. The subcutaneous tissue of the

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palmar aspect of the terminal phalanges is connected by fibrous processes with the periosteum; hence the frequency of necrosis of the terminal phalanx in suppurative inflammations in this region.

THE LOWER EXTREMITY.

THE BUTTOCK..

The region of the hip or buttock extends from the crest of the ilium above to the gluteal fold below. The highest point of the iliac crest, situated a little posterior to its middle, is on a level with the fourth lumbar spine; the anterior superior spine of the ilium is directed forwards, and belongs to the groin, which it limits laterally; the posterior superior spine, situated at the bottom of a dimple or small depression, is on a level with the second sacral spine, and corresponds, therefore, to the middle of the sacro-iliac joint. Two and a half inches. behind the anterior superior spine is a prominence upon the outer lip of the iliac crest; this prominence, which is termed the tubercular point, is the most lateral part of the crest, and has been referred to in dealing with the surface anatomy of the abdomen. A hand's breadth below the tubercle of the crest is the greater trochanter of the femur, the most lateral bony landmark of the hip; its anterior and posterior borders are best felt between the fingers and thumb, while the limb is slightly abducted to relax the ilio-tibial tract, and if the thigh is now rotated, it will be noted that the trochanter rotates round the segment of a circle, the radius of which is formed by the head and neck of the femur; in nonimpacted fractures of the neck of the femur the trochanter rotates round the segment of a much smaller circle. Nelaton's line, drawn from the anterior superior spine to the most prominent part of the ischial tuberosity, crosses the hip at the level of the proximal border of the greater trochanter; this line is employed to ascertain the presence or absence of upward displacement of the trochanter. Chiene demonstrates the relative height of the trochanters by stretching two tapes across the front of the pelvis, one between the anterior superior spines, and the other between the proximal borders of the trochanters; the lower tape will converge towards the upper on the side of the upward displacement. A line prolonging the anterior border of the greater trochanter vertically upwards touches the iliac crest at the tubercular point. The sciatic tuberosity, in the erect posture, is overlapped by the distal border of the gluteus maximus; its most prominent part is felt a little proximal to the medial part of the gluteal fold. If the hip is rotated medially, the lesser trochanter of the femur may be felt by deep palpation proximal to the lateral end of the gluteal fold; it corresponds to the interval between the distal border of the quadratus femoris and the proximal border of the adductor magnus, and therefore, also, to the level of the medial circumflex artery of the thigh.

The lower border of the gluteus maximus lies a little above the gluteal fold medially, crosses it about its middle, and is continued distally and laterally to meet the proximal end of the furrow of the lateral intermuscular septum, at the junction of the proximal and middle thirds of the femur. The medial borders of the two great gluteal muscles are separated by the deep gluteal cleft, which extends upwards and backwards from the perineum to the level of the fourth sacral spine, where it opens out into the triangle upon the back of the sacrum. Anteriorly the buttock is limited by the prominence of the tensor fascia latæ muscle, which extends distally and somewhat backwards from the anterior end of the crest, to join the ilio-tibial tract distal to the root of the greater trochanter.

The superior gluteal artery reaches the buttock immediately below the upper border of the greater sciatic foramen, opposite a point corresponding to the junction of the upper and middle thirds of a line drawn from the posterior superior iliac spine to the upper border of the greater trochanter. To expose the vessel the incision should be made along this line, which has the advantage of running parallel to the fibres of the gluteus maximus, as well as parallel to the interval between the gluteus medius and piriformis muscles.

The sciatic nerve enters the buttock at a point corresponding to the junction of the upper and middle thirds of a line drawn from the superior posterior iliac spine to the sciatic tuberosity; from this point the nerve passes downwards and slightly laterally upon the ischium to a point midway between its sciatic tuberosity and the greater trochanter. The spine of the ischium and the pudendal vessels are situated opposite the junction of the lower and middle thirds of the above line. The vessels and nerves which enter the buttock through the greater sciatic foramen below the piriformis, may be exposed through an incision below and parallel to that above described for exposing the superior gluteal artery, viz., an incision corresponding to the middle two-fourths of a line extending from the upper end of the gluteal cleft to the root of the greater trochanter; the deep landmarks are the lower border of the piriformis and the root of the sciatic spine.

THE BACK OF THE THIGH

The hamstring muscles, and especially the tendon of the biceps and semitendinosus, are thrown into prominence either by standing on tiptoes with the knees slightly flexed, or by flexing the leg against resistance. By throwing the

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FIG. 1118.-SECTION THROUGH THIGH AT THE LEVEL OF THE PROXIMAL PART OF THE ADDUCTOR CANAL

hamstrings into action, the line of the lateral intermuscular septum of the thigh is indicated by a well-marked furrow, extending from the lower edge of the insertion of the gluteus maximus to the lateral aspect of the knee; behind this furrow is the biceps femoris, and in front of it is the large vastus lateralis, covered by the strong ilio-tibial tract of the fascia lata. The shaft of the femur may be cut down upon along the whole length of this furrow with least injury to the soft parts; the popliteal surface of the femur and deep-seated popliteal abscesses are most conveniently reached through the lower part of the same incision.

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extending from a point midway between the sciatic tuberosity and the greater trochanter to the centre of the popliteal fossa. The nerve enters the thigh under cover of the lateral border of the biceps, whereas the posterior cutaneous nerve of the thigh which takes the same line, descends superficial to the biceps, between it and the fascia lata. In the operation of stretching the sciatic nerve it is cut down upon immediately distal to the lower border of the gluteus maximus. The surgeon, standing on the side of the patient opposite to the leg to be operated upon (Chiene), makes an incision in the line of the nerve through the integuments and fascia lata, and, sweeping the index-finger round the lateral border of the

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FIG. 1119.-SECTION THROUGH THE THIGH IMMEDIATELY PROXIMAL TO THE PATELLA.

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The common peroneal nerve may be rolled under the finger as it passes distally immediately behind the tendon of the biceps and the head of the fibula; so close is the nerve to the tendon that the tendon should be divided, in cases where this is necessary, by the open method rather than subcutaneously.

Abscesses may reach the flexor compartment of the thigh from various sources, viz.: (1) from the posterior aspect of the hip-joint; (2) from the pelvis, through the greater sciatic foramen; (3) from one or other of the burse under the gluteus maximus; (4) from the front of the hipjoint, by passing backwards under the tensor fascia lata; or by winding backwards beneath the neck of the femur, and through the interval between the quadratus femoris and the adductor magnus; (5) from the iliac fossa under the inguinal ligament into the fascial trigone, and thence to the back of the thigh by one or other of the routes already mentioned; (6) the pus may spread proximally from the popliteal surface of the femur, the knee, a popliteal gland, or from a bursa.

THE POPLITEAL FOSSA.

When the knee is extended the popliteal fascia is put upon the stretch, and obliterates the hollow of the popliteal fossa; by flexing the knee the fascia is relaxed, and the fingers may be pressed deeply into the proximal or femoral

division of the fossa; as a rule, the pulsations of the popliteal artery can be felt. Deep to the semitendinosus is the fleshy semimembranosus, which bulges into the space and overlaps the proximal part of the popliteal artery. Between the semimembranosus and the medial head of the gastrocnemius is the most important bursa in the popliteal region; it not infrequently becomes distended with fluid, and then presents usually a more or less sausage-shaped outline; according to Holden, the bursa communicates with the cavity of the knee-joint in one subject out of five.

To map out the line of the popliteal vessels and the tibial nerve, draw a line

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FIG. 1120.-THE THIGH AND GROIN.

from a point a little medial to the proximal angle of the space to a point midway between the condyles of the femur, and thence distally along the middle of the space to the level of the distal part of the tuberosity of the tibia. The tibial nerve lies immediately under cover of the deep fascia; the artery is separated from the popliteal surface of the femur by a quantity of fat. The popliteal lymph glands lie deep to the popliteal fascia, one upon the tibial nerve, the others deeply in the space (Leaf).

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THE FRONT OF THE THIGH.

Between the front of the thigh and the abdomen is the fold of the groin, at the bottom of which the inguinal ligament can be felt as a tense band, stretching from the anterior superior spine of the ilium to the pubic tubercle. The anterior superior spine looks directly forwards; comparative measurements of the inferior extremities are made by stretching a tape from it to the tip of one or other of the malleoli, care being taken that the pelvis is horizontal, and the limbs in corresponding positions. The pubic tubercle is felt under the proximal and lateral part of the mons Veneris and at a corresponding point in the male; between the tubercle and the symphysis is the crest of the pubis, the two crests together

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