THE MUSCULAR SYSTEM 283 



the pronator quadratus. An additional muscle is the brachioradialis, 

 which, although belonging with the extensor group, has come to have 

 flexor action. Altogether there are nineteen muscles in the forearm. 



Besides these muscles of the forearm most of which act upon the hand, 

 there are nineteen intrinsic to the hand. Four of these are inserted on 

 the thumb, the abductor pollicis brevis, opponens pollicis, flexor pollicis 

 brevis, and adductor pollicis. Three muscles are inserted on the little 

 finger, abductor, flexor brevis, and opponens digiti minimi. In the palm 

 of the hand are four lumbrical and seven interosseus muscles. The 

 palmaris brevis is usually considered an integumentary muscle like those 

 of the face. 



Hip Muscles. The muscles of the hip, like those of the shoulder, 

 may be divided into dorsal and ventral sets. The dorsal muscles have 

 their origin on the vertebral column and the ilium. Of these, the ilio- 

 psoas protracts the thigh, and the gluteus maximus extends it. Other 

 dorsal muscles, are the gluteus medius, gluteus minimus, piriformis, 

 and tensor fasciae latae, all of which are inserted on the femur. 



The ventral muscles of the hip have their origin on the pubis and the 

 ischium, and their insertion on the femur. Among them are the obturator 

 extemus, obturator intemus, quadratus femoris, and the gemelli, all of 

 which both adduct and rotate the thigh. The obturator externus, here 

 included in the hip muscles is sometimes regarded as a thigh muscle. 



Muscles of the Thigh. There are three groups of thigh muscles, 

 anterior — extensor, medial — adductor, and posterior — flexor muscles. 

 Their relations are such that they act upon both the thigh and the lower 

 leg. 



The anterior extensor group includes five muscles, the sartorius or 

 "tailor muscle," and the four divisions of the quadriceps femoris, the 

 rectus femoris, vastus lateralis, vastus medialis, and vastus intermedins. 

 In the medial adductor group are five muscles, gracilis, pectineus, adductor 

 brevis, adductor longus, and adductor magnus. The posterior or "ham- 

 string" muscles which bend the leg and extend the thigh, are the semi- 

 tendinosus, semimembranosus, and biceps femoris. 



Muscles of the Lower Leg and Foot. There are thirteen muscles 

 in the lower leg, four of which form an anterior group which bends the 

 ankle and hfts the toes, the tibialis anterior, extensor digitorum longus, 

 peroneus tertius, and extensor hallucis longus. Two lateral muscles, 

 the peroneus longus and brevis, extend the foot. Three superficial calf 

 muscles, the gastrocnemius, soleus, and plantaris, connect with the 

 calcaneus by the tendon of Achilles, and extend the foot. Beneath them 

 are four deeper muscles, the popliteus, which rotates the leg medially, 

 and the flexor digitorum longus, flexor hallucis longus, which bend the 

 toes, and tibialis posterior, which extends the foot. 



