FUNCTIONS OF MUSCLES 505 



(c) To flex all joints: flexor poUicis longus; the carpo-metacarpal and metacarpo- 



phalangeal joints; flexor brevis, the adductors, abductor brevis; 

 the carpo-metacarpal joints : opponens poUicis, abductor longus. 



(d) To extend: all joints, extensor poUicis longus; the carpo-metacarpal and 



metacarpo-phalangeal joints, extensor poUicis brevis; the inter- 

 phalangeal joint, abductor brevis, flexor brevis. 



(e) To adduct: the adductor, flexor brevis, opponens, first dorsal interosseous, 



extensor longus. 

 (/) To abduct: the long and short abductors. 



19. Muscles acting on the fingers. 



(a) To flex: all the joints, flexor digitorum profundus; all but the last, flexor digito- 



rum sublimis; the metacarpo-phalangeal joint only, flexor 

 digiti quinti brevis, the lumbricales, and interossei. 



(b) To extend the fingers: extensor digitorum communis, extensor indicis pro- 



prius, extensor digiti quinti proprius; to extend the two inter- 

 phalangeal joints: the lumbricales, interossei, and frequently the 

 flexor digiti quinti brevis. 



(c) To abduct from the axis passing through the centre of the middle finger: 



dorsal interossei, first two lumbricales, abductor digiti quinti, 

 the long extensor of the fingers. 



(d) To adduct toward this axis: volar interossei, last two lumbricales, opponens 



and flexor digiti quinti brevis. 



20. Muscles acting on the pelvis. 



(o) To flex it: rectus abdominis, obUquus abdominis externus and internus, 

 psoas major and minor. 



(b) To extend it: sacro-spinalis, multifidus, latissimus dorsi and quadratus 



lumborum. 



(c) To bend it laterally and rotate it: abdominal muscles, quadratus lumbo- 



rum, psoas muscles, and latissimus dorsi acting on one side. 



21. Muscles acting on the thigh at the hip-joint (arranged according to R. Fick). 



(a) To flex it: ilio-psoas, rectus femoris, adductor longus, adductor brevis, 

 obturator externus, tensor fasciae latse, pectineus, sartorius, 

 gluteus minimus, adductor magnus (upper part), gi-acilis, 

 quadratus femoris. 



(6) To extend it: gluteus maximus, adductor magnus (posterior lower part), 

 biceps, semitendinosus, semimembranosus, gluteus medius, 

 piriformis, obturator internus. 



(c) To adduct it: adductor magnus, gluteus maximus, adductor brevis, adductor 



longus, quadratus femoris, obturator externus, gracilis, ad- 

 ductor magnus (upper part), pectineus, biceps, semitendinosus, 

 obturator internus and gemelU, semimembranosus. 



(d) To abduct it: gluteus medius and minimus, the piriformis, rectus femoris, 



tensor fasciae latae, sartorius; and when the hip is flexed, the 

 gluteus maximus, obturator internus, and gemeUi. 



(e) To rotate it medialward: gluteus medius (anterior portion), gluteus minimus, 



iUo-psoas, adductor magnus (upper part), pectineus, adductor 

 longus, semitendinosus, semimembranosus, tensor fasciae 

 latae. 

 (/) To rotate it lateralward: gluteus maximus, quadratus femoris, obturator 

 internus, piriformis, rectus femoris, adductor brevis, adductor 

 magnus (lower part), biceps, sartorius, obturator externus 

 graciUs, gluteus medius (posterior part). 



22. Muscles acting on the leg at the knee-joint (arranged according to R. Fick). 



(a) To flex it: semimembranosus, semitendinosus, biceps, gastrocnemius, 



gracilis, sartorius, popUteus. 



(b) To extend it: quadriceps femoris (the tensor fasciae latae and gluteus maxi- 



mus through the iKo-tibial band keep the extended leg fixed). 



(c) To rotate it medialward (when flexed) : semimembranosus, semitendinosus, 



sartorius, popliteus, gracilis. 



(d) To rotate it lateralward (when flexed) : biceps, tensor fasciae latae. 



23. Muscles acting on the foot at the ankle-joint (arranged according to R. Fick). 



(a) To flex it: tibiahs anterior, extensor digitorum longus, peroneus tertius, 



extensor hallucis longus. 



(b) To extend it: gastrocnemius, soleus, flexor hallucis longus, peroneus longus, 



tibiaUs posterior, flexor digitorum longus, peroneus brevis. 



(c) To invert the foot at the inferior articulation of the talus (art. talo-calcanea 



and talo-calcaneo-navicularis): gastrocnemius, soleus, tibialis 

 posterior, flexor haUucis longus, flexor digitorum longus, tibiaUs 

 anterior. 



(d) To evert the foot at the inferior articulation of the talus : peroneus longus, 



peroneus brevis, extensor digitorum longus, peroneus tertius, 

 extensor hallucis longus, tibialis anterior. 



(e) To invert the foot at Chopart's (talo-navicular-calcaneo-cuboid) joint: 



tibiaUs anterior, tibiaUs posterior, flexor digitorum longus, 

 flexor haUucis longus, extensor haUucis longus. 

 (J) To evert the foot at Chopart's joint: peroneus longus, peroneus brevis, 

 extensor digitorum longus, peroneus tertius. 



