factory view of the muscle may be obtained. It will then become evident that numerous fleshy fibres arise from the deep surface of the fascia. Care must be taken not to injure the origin of the tensor fascia femoris which overlaps the anterior part of the gluteus medius, and is partially adherent to it.

Gluteus Medius.-The gluteus medius arises from that part of the dorsum ilii which is bounded above by the superior curved line and the anterior four-fifths of the crest of the ilium, and below by the middle curved line; it also derives fibres from the strong fascia which covers its upper and anterior part. The fibres converge to form a flattened band, partly fleshy and partly tendinous, which is inserted into an oblique line on the outer aspect of the great trochanter of the femur, as well as into the surface immediately above it.

Dissection.—The gluteus medius must now be reflected. This dissection is complicated by the fact that in its upper and anterior part the gluteus medius is partially blended with the subjacent gluteus minimus and the tensor fasciæ femoris. Begin by rotating the limb well outwards. Then seizing the gluteus maximus with left hand, pull it well outwards, and divide the glistening aponeurosis into which it is inserted for two or three inches in a downward direction. This will bring very conspicuously into view the upper part of the vastus externus. Next, grasp the cut edge of the fascia lata from which the gluteus maximus has been separated, and, dragging it forcibly outwards, dissect in the interval between it and the gluteus medius. The tensor fascia femoris, which is intimately associated with this portion of the fascia lata, is pulled outwards with it, and the deep surface of that muscle clothed by a strong deep lamella of fascia comes into view. Very little dissection is required to expose its nerve of supply-a branch from the superior gluteal-which emerges from the anterior border of the gluteus minimus, and sinks into its deep surface. An artery will also be noticed ramifying on the deep surface of the tensor fasciæ femoris; this is the ascending branch of the external circumflex. Seeing that the anterior borders of the gluteus medius and gluteus minimus are adherent, it is well to separate them from behind forward by introducing the fingers between their posterior borders. When the gluteus medius is completely isolated, it may be divided about two inches above the great trochanter of the femur, and the two portions thrown respectively upwards and downwards. A small bursa between the muscle and the upper part of the great trochanter will thus be brought into view, and the exact insertion of the tendon will be rendered evident. As the upper part of the muscle is raised, a

number of vessels and nerves between it and the gluteus minimus will be exposed. These must be carefully cleaned and followed to their destinations. They are derived from the gluteal artery and the superior gluteal nerve.

Gluteal Artery (arteria glutea superior).-This is a large vessel which escapes from the pelvis through the upper part of the great sacro-sciatic foramen above the level of the pyriformis.

Immediately after its exit, it divides into a superficial and a deep division. The superficial division has been already seen during the reflection of the gluteus maximus. It is distributed to the deep surface of that muscle, and is placed between it and the gluteus medius.

The deep division bifurcates close to its origin into a superior and an inferior branch; both of these lie between the gluteus medius and minimus. The superior branch follows accurately the middle curved line on the dorsum ilii, and at the anterior superior spine terminates by anastomosing with the superficial and deep circumflex iliac arteries, and with the ascending branch of the external circumflex. The latter has already been noticed passing upwards under cover of the tensor fasciæ femoris. The inferior branch runs downwards and forwards towards the great trochanter. It gives twigs to the two gluteal muscles between which it lies, and some terminal offsets to the hip-joint.

The Superior Gluteal Nerve (nervus glutæus superior) emerges from the pelvis in company with the gluteal artery, and passing forwards between the gluteus medius and minimus, gives branches to both these muscles. Its terminal branch pierces the anterior fibres of the gluteus minimus, and ends in the tensor fasciæ femoris.

The Gluteus Minimus arises from the broad area on the dorsum ilii, which is included between the middle and inferior curved lines. The muscular fibres pass gradually into an aponeurotic tendon, which covers the superficial surface of the lower part of the muscle. This tendon as it descends narrows into a flattened band, which is inserted into a special impression on the anterior aspect of the

great trochanter of the femur. It is intimately connected at its insertion with the capsule of the hip-joint.

Parts under cover of the Gluteus Minimus.—The last step in the dissection of the gluteal region consists in the reflection of the gluteus minimus muscle. It must be detached from its origin and thrown downwards. Three objects are revealed by this dissection (1) the capsular ligament of the hip-joint; (2) a bursa which intervenes between the tendon of the muscle and the great trochanter; (3) the reflected tendon of the rectus femoris.

The capsular ligament will be seen to be only loosely attached to the posterior aspect of the neck of the femur, but very firmly to the acetabular brim. The synovial bursa should be opened and examined. The reflected tendon of

the rectus femoris occupies a groove situated just above the upper margin of the acetabulum. It is partially concealed by some fibres of the capsular ligament, which are prolonged upwards over it. It should be cleaned by repeatedly drawing the point of the knife over it in a direction parallel to its fibres.

POPLITEAL SPACE.

Before the muscles on the back of the thigh are disturbed, it is well to dissect the popliteal space. In this way the boundaries of the space are maintained in position during our examination of the structures which lie within it.

During the dissection of the popliteal space the following structures are brought into view :—

6. The internal and external popliteal nerves and their branches. 7. The popliteal artery and vein and their branches.

8. A few lymphatic glands.

9. A slender branch from the obturator nerve. 10. The popliteus muscle.

Surface Anatomy.-The space which lies immediately above the knee-joint, and between the hamstring muscles, is termed the ham. It is depressed when the knee is flexed, but forms a slight prominence when the joint is fully extended. By pressing deeply into the interval between the hamstrings, the (injected) popliteal artery may be distinguished, and its pulsations can sometimes be distinguished in this situation in the living subject. The tendon of the adductor magnus can be readily detected on the inner side of the limb, and should be traced downwards to the adductor tubercle on the inner condyle of the femur. It can be rendered distinct by slightly flexing the knee-joint, and at the same time forcibly abducting the limb. The tuberosities of the femur may be seen and felt: the internal is the more prominent of the two. The articulation between the femur and the head of the tibia can seldom be seen, but can always be felt. Below the kneejoint the head of the fibula forms a prominence on the outer side, and, by flexing the knee and pressing deeply between the fibula and the external condyle of the femur, the cord-like external lateral ligament can be distinguished. The external popliteal nerve may be felt as it crosses the outer side of the neck of the fibula, just before it pierces the peroneus longus muscle. The two heads of the gastrocnemius form prominent objects in muscular subjects.

The back of the thigh presents a smooth, rounded surface. In thin subjects indications of the bellies of the hamstring muscles may be seen.

Reflection of Skin.-Before beginning the dissection a good-sized block should be placed under the knee so as to support the limb and render the muscles which bound the space tense. Incisions-(1) a vertical incision along the middle line of the limb, beginning about five inches above, and terminating about four inches below, the bend

of the knee; (2) a transverse incision at the upper end of the mesial incision; (3) a transverse incision at the lower extremity of the mesial incision. The two transverse incisions should extend almost half-way round the limb.

Two flaps of skin are thus mapped out, and these must be raised and thrown, the one inwards and the other outwards.

Superficial Fascia External Saphenous Vein-Branches of Small Sciatic Nerve. The fatty layer upon which the skin rests is now brought into view, and the cutaneous nerves and vessels must be secured. First look for a small nerve-a branch of the small sciatic-which passes downwards over the space near the middle line, and when this is found, dissect out the external saphenous vein. This vessel ascends in the middle line of the leg, and on tracing it upwards it will be found to disappear from view by piercing the deep fascia, and entering the lower part of the popliteal space. The terminal branch of the small sciatic nerve pierces the popliteal fascia at the lower part of the space, and here it will be seen lying close to the external saphenous vein.

In removing the superficial fascia care must be taken of the deep popliteal fascia which is somewhat thin.

Popliteal Fascia. Although thin, the deep fascia possesses considerable strength, owing to the transverse fibres which are interwoven amidst its proper aponeurotic fibres. In removing this fascia the dissector will notice that it is firmly attached on each side to the tendons of the muscles which bound the popliteal space. Above it is continuous with the fascia lata of the thigh.

Before opening up the popliteal space the dissector is recommended to read the two following paragraphs, which deal generally with its contents and boundaries.

Contents of the Space. The principal objects within the popliteal space are the popliteal artery and vein with their branches. They are placed deeply in the space, and in close contact with each other-the vein being superficial to the artery throughout. The two popliteal nerves