View of the muscles that bend the thigh. 1. The
muscle called psoas; 2. the muscle called iliacus; 3. tendons
of these muscles, going to be inserted into the trochanter
minor of the femur.
204. The muscles that extend the thigh, or that carry it backwards, named the glutæi, the most powerful muscles of the body, are placed in successive layers, one upon the other, on the back part of the ilium (fig. C. 1, 2, 3), and are inserted into the linea aspera of the femur. They constitute the mass of flesh which forms the hip, and their powerful action in drawing the thigh backwards is assisted by several other muscles (fig. C. 4, 5, 6). Their action is never perfectly simple and direct; for those which move the thigh forwards sometimes carry it inwards, and sometimes outwards; and in like manner, those which move it backwards, at one time carry it inwards and at another outwards, according to the direction of the fibres of the muscle and the position of the limb when those fibres act; while some of them, and more especially those which carry it backwards, at the same time rotate it, or roll it upon its axis.
View of the muscles that extend the thigh. 1. The
muscle called glutæus maximus, removed from its origin,
2, 2, to show the muscles which lie beneath it; 2. cut edge
showing the origin of the same muscle; 3. the muscle
called glutæus medius; 4, 5, 6. smaller muscles, assisting
the action of the glutæi.
205. The knee is a hinge-joint, admitting only of flexion and extension, and is therefore provided only with two sets of muscles, one for bending and the other for extending the leg. The flexors of the leg arise from the under and back part of the pelvis, are seated on the back part of the thigh, and are inserted into the upper part either of the tibia or of the fibula (fig. CI). They consist for the most part of three muscles, named the semi-tendinosus, the semi-membranosus (fig. CI. 3), and the biceps of the leg (fig. CI. 1). The tendons of the two former muscles, in passing to be inserted into the leg, form the inner, and that of the latter the outer, hamstrings (fig. CI. 4, 5).
View of the flexor and extensor muscles of the leg.
1. The biceps of the leg; 2. tendon of the biceps, inserted
into the head of the fibula; 3. the semi-membranosus,
passing to be inserted into the head of the fibula; 4. tendon
of the semi-membranosus forming the inner, and
5. tendon of the biceps forming the outer, hamstring;
6. upper part of the gastrocnemius muscle; 7. the four large
muscles which unite to form the great extensor muscle of
the leg, inserted into 8. the patella; 9. a portion of the
glutæus maximus concealing the other muscles of the hip.
206. Four large muscles, blended together in such a manner as to form one muscle of prodigious size, termed the quadriceps cruris (fig. CI. 7), occupying nearly all the forepart and the sides, and a considerable portion of the back part of the thigh, constitute the great flexor of the thigh. This enormous mass of muscle arises partly from the ischium, and partly from the upper part of the femur (fig. CI. 7), and is all inserted into the patella (fig. CI. 8), which constitutes a pulley for the purpose of assisting the action of these powerful muscles.
207. The muscles which bend the toes and extend the foot, termed the gastrocnemii (fig. CII. 1, 2), are placed on the back part of the leg, and form the mass of muscle which constitutes the calf of the leg (fig. CII. 1, 2). They arise partly from the lower extremity of the femur (fig. CII.) and partly from the upper and back part of the fibula and tibia; and they form the largest and strongest tendon in the body, termed the tendo achillis (fig. CII. 3), which is implanted into the heel (fig. CII. 4).
