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Show 4/6 DR. R. W. SHUFELDT ON [Nov. 16, The patella is found encased in front in this great tendinous sheath of the knee-joint, and below the apex of this sesamoid we find the enveloped track of the tendon of the ambiens muscles, as it passes round in front of the femoro-tibial articulation. The combined tendon of the extensor femoris is finally inserted into the cnemial crest of the tibial and the lateral boundaries of the summit of that bone. Some of the superficial muscles on the outer side of the leg are so extended as to take a certain amount of their origin from this great tendinous expansion. In Plate XLIV. fig. 2 I have very thoroughly divided these two subdivisions of the extensor femoris, in order to show their relative size, as well as their relation to each other and the surrounding structures. The biceps flexor cruris (Plate XLIV. fig. 1 ; fig. 2, Bi) arises by carneous fibres upon quite an extensive portion of the under surface of the over-curled part of the ilium behind the acetabulum, and by a long tendinous slip which comes off from the free anterior margin of this part of the ilium. The fibres converge as they pass downwards, and unite to form a somewhat flattened muscle. Opposite the head of the tibia, the biceps terminates in a round tendon, of cord-like dimensions, which passes through a special loop to make its way between some of the muscles at the back of the leg, to become inserted on the tubercle intended for it on the outer side of the superior moiety of the shaft of the fibula. The loop of the biceps (Plate X L V . fig. 1,1) is flat and fashioned like a delicate tendinous ribbon. Its upper end arises from the side of the shaft of the femur above the external condyle, while the lower end comes off from this protuberance just below the insertion of the outer slip of the external head of the gastrocnemius muscle. A branch of the sciatic nerve also passes through this loop in company with the tendon of the biceps. The semitendinosus (Plate XLIV. figs. 1,2, St; Plate X L V . fig. 1, St) is a marvellously well-developed muscle in this form, as is also its accessory head. Its origin fills about three fourths of the nether cavity formed by the posterior overarching portion of the ilium, under which it arises. Posteriorly, the fibres forming its free margin are so arranged as to create a rounded border ; the lower end of its arc terminating about opposite the post-pubis of the pelvis. From this origin the fibres of the semitendinosus pass downwards and forwards as a great, though somewhat compressed muscle. When within rather more than a centimetre's length of the shaft of the femur, they terminate in an oblique tendinous raphe, which latter forms the boundiug-line between this muscle and the next. The accessory semitendinosus (Plate X L V . fig. 1, a.s.t) is composed of coarser fibres than the muscle just described. It springs from a longitudinal line occupying the distal half of the shaft of the femur, and from the upper surface of the hinder aspect of the external condyle of that bone. The fibres pass backwards and a little upwards to become inserted into the tendinous raphe just alluded to. The lower extremity of this tendinous raphe terminates, in Geococcyx, in a thin, flat, and delicate tendon, which continues down- |