OCR Text |
Show 628 MR. A. H. G A R R O D O N [June 17, Tensor fasciae.-This is the superficial muscle of the outside thigh, covering the femur. It is flat and triangular in shape, and arises as a membranous expansion which covers the gluteus ii., from the lower two thirds of the posterior border of the iliac fossa in which that muscle is situated, and from the fibrous septum which separates that muscle from the gluteus iii. Further down it has origin also from the whole length of the ridge which separates the postacetabular area from the external lateral surface of the ischium, and which m a y be termed the postacetabular ridge, as well as from the posterior border of the ischium, as far forwards as its junction with the pubis, being here slightly overlapped by the semitendinosus. The fibres converge towards the knee ; and the deep portion of the muscle blends in its course with the vastus externus, together with which it continues forward to become part of the broad thin tendon which covers the knee and is inserted in the front of the tibia-head, the patella being situated in it, together with the long, slender, and flat tendon of the ambiens muscle, which is situated below it, running obliquely from inside and above, outwards and downwards. In many birds, as the Falconidae and Psittaci, this muscle does not extend below the level of the femur, but ends inferiorly by blending with the vastus externus ; and consequently, where such is the case, it evidently cannot, as it does otherwise, cover any of the flexors of the leg. In the Bucerotidae it is entirely absent. Whether this postacetabular portion of the tensor fasciae is present or absent has some bearing on classification, as in the different families it is a very constant feature. Biceps cruris.-The anterior portion of this muscle m a y be seen in the Fowl's leg before the tensor fascise has been removed, just below it, near its insertion. This muscle is mostly covered by the tensor fasciae, arising from the upper three fourths of the postacetabular ridge, just in front of the origin of that muscle. Its fibres converge to form a round tendon, which in the outer side of the popliteal region is bent sharply downwards by passing through a tendinous sling which arises from the lower end of the femur, to be inserted on a prominence on the outer side of the fibula, about half-wajr down the leg. In the loop above this tendon, and consequently quite out of the way of compressing forces, one of the nerves to the leg and foot is continued. In one or two birds, as Phaethon, the biceps does not pass through any loop, but is inserted directly by a broad flat tendon into the upper part of the fibula. Semitendinosus.-This flat ribbon muscle runs nearly parallel with the lower fibres of the biceps, just below it. Its origin is mostly from the tip of the transverse process of the first free coccygeal vertebra, and from the fibrous membrane between it and the inferior oorder of the ilium. Near its origin it, being superficial, curves over the posterior inferior angle of the ilium, and covers the inferior fibres of origin of the tensor fasciae, running upwards and forwards towards the inner side of the head of the tibia, and so getting covered anteriorly by the inserted end of the biceps. A rhomboidal sheet of muscle, arising from the anterior end of the linea aspera, descends to form an accessory head to this muscle, joining it anteriorly, on its outer side, by an oblique tendinous raphe, which continues down the |