ADDUCTOR MUSCLES 471 



Tendon of the quadriceps. — The quadriceps tendon may be more or less distinctly divided 

 into layers, of which the superficial layer belongs to the rectus, the deep to the vastus inter- 

 medius, and the intermediate to the vastus lateraUs and mediahs. Some of the more superficial 

 fibres of the tendons of the two vasti, however, cross in front of the rectus tendon. The com- 

 bined tendon of the quadriceps is in part attached to the superior and lateral margins of the 

 patella, and in part extends over the patella into the patellar ligament. A part of the tendon 

 fibres of the vastus lateralis and medialis run on each side of the patella to the ventral surface of 

 the condyles of the tibia. These form the retinacula patellae mediate and laterale. The medial 

 is the broader and better developed. With the retinacula are included bundles of fibres which 

 run from the epicondyles to the patella and into which some muscle fibre-bundles are inserted. 

 From the apex of the patella to the tuberosity of the tibia the quadriceps tendon is continued 

 as the patellar ligament (fig. 415). 



Nerve-supply. — The relations of the branches of distribution to the various parts of the 

 muscle have been pointed out above in connection with each head. The general relations of 

 these branches of the femoral nerve are as follows: — From the femoral nerve near the proximal 

 end of the va8tus medialis the branches for the vastus lateralis, vastus intermedins (crureus), and 

 rectus pass distally and laterally between the rectus and vastus intermedius (crureus) to be 

 distributed to the muscles named, while the chief nerve for the vastus medialis descends on the 

 medial side of this muscle in company with the saphenous nerve. The branches to the vastus 

 lateralis and intermedius are commonly bound up in a single nerve-trunk for some distance. 

 The branches to the rectus are usually bound up with this trunk for a shorter distance. The 

 nerve to the vastus medialis may be united to this trunk for a slight distance, but more 

 frequently it is more or less bound up with the saphenous nerve. 



Action. — The quadriceps is the extensor of the leg. The rectus femoris also flexes the thigh 

 at the hip and is a weak abductor of the thigh. The articularis genu makes tense the capsule 

 of the knee-joint. 



Relations. — The quadriceps is covered ventrally immediately by the fascia lata. The 

 sartorius runs along its medial margin; the tensor fasciae latse lies over the proximal quarter 

 of its lateral surface. Dorsal to the vastus lateralis he the gluteus maximus and biceps; dorso- 

 medial to the vastus medialis, the three adductor muscles and the semimembranosus. Next 

 the vastus medialis lies the adductor canal with the femoral vessels and the saphenous nerve. 



Variations.— The variations of this muscle, aside from a greater or less fusion of its parts, 

 are not marked. The attachment of the rectus femoris to the anterior inferior spine, which 

 takes place in the embryo later than its insertion above the acetabulum, may be wanting. On 

 the other hand, this tendon may extend to the anterior superior spine. Occasionally the deep 

 reflected tendon may be wanting. The rectus accessorius is a fasciculus rarely found, which 

 arises by a tendon from the rim of the acetabulum and is inserted into the ventral edge of the 

 vastus lateralis. It is innervated by a twig from the branch to the rectus. 



BURS^ 



B. m. recti femoris (superior). — A small bursa between the deep tendon of the rectus 

 femoris and the edge of the acetabulum. Rare. B. m. recti femoris (inferior). — Between 

 the tendon of the rectus and the combined tendon of the vastus lateralis and medialis. _ Oc- 

 casional. B. praepatellaris subtendinea. — A bursa between the tendon of the quadriceps 

 and the periosteum of the patella. Of the three praepatellar bursae — the subcutaneous, sub- 

 fascial, and subtendinous — as a rule only one occurs. When two or three exist, they usually 

 communicate freely with one another. B. suprapatellaris. — A bursa between the anterior 

 surface of the lower end of the femur and the tendon of the quadriceps. It usually communi- 

 cates with the joint cavity. B. infrapatellaris profunda. — A bursa between the patellar liga- 

 ment and the tibia. It seldom communicates with the joint cavity. B. m. sartorii propria. 

 — A bursa, fairly large, between the tendon of the sartorius and the tendons of the semitendi- 

 nosus and gracilis muscles. This usually communicates with the bursa anserina (see p. 474). 



2. The Medial (Adductor) Group 



(Figs. 409, 411, 412) 



To this group of muscles belong the gracilis, the pectineus, the adductors brevis, 

 longus, and magnus, and the obturator externus. The most superficial of the 

 group is the gracilis (figs. 408, 411). This ribbon-shaped muscle arises from the 

 inferior pubic and ischial rami, extends along the medial side of the thigh, and 

 gives rise to a tendon which curves forward from behind the medial condyle of 

 the femur to be inserted under the tendon of the sartorius into the medial side of 

 the upper extremity of the tibia. The quadrilateral pectineus arises from the 

 body and superior ramus of the pubis; the triangular adductor longus from the 

 superior ramus medial to this (fig. 411). The pectineus is inserted into the 

 pectineal fine of the femur; the adductor longus into the middle third of the linea 

 aspera. The triangular adductor brevis (fig. 412) arises from the inferior pubic 

 ramus below the adductor longus. It is inserted into the pectineal line and the 

 upper third of the hnea aspera. The large, triangular adductor magnus (figs. 

 409, 412) arises from the inferior ramus and the tuber of the ischium and is 



