Fig. 2. Ventral views of the lumbosacral plexus...Fig. 2.Ventral views of the lumbosacral plexus ofTympanuchus pallidicinctus. Sympathetic ganglionated chain removed. Numbers indicate synsacral spinal nerves. × 2. A. T.p. 1L. B. T.p. 2L.
Fig. 3. Ventral views of the lumbosacral plexus...Fig. 3.Ventral views of the lumbosacral plexus. Sympathetic ganglionated chain removed. Numbers indicate synsacral spinal nerves. × 2. A.Tympanuchus cupido pinnatus3L. B.Pedioecetes phasianellus jamesi4L.
Fig. 4. Semidiagrammatic ventral views of the femoral nerve,...Fig. 4.Semidiagrammatic ventral views of the femoral nerve, showing the distribution of the branches. × 3. 1,2, M. extensor iliotibialis anticus; 3, cutaneous; 4-6, M. extensor iliotibialis lateralis; 7,8, M. iliacus; 9, M. gluteus profundus; 10-12, fused Mm. vastus lateralis and vastus medialis; 13,14, M. vastus medialis; 15, M. ambiens; 16, M. femoritibialis internus; 17, nonmuscular; 18, M. psoas; 19, M. iliotrochantericus medius. A.Tympanuchus cupido pinnatus3L. B.Pedioecetes phasianellus jamesi3L.
Fig. 5. Semidiagrammatic ventral views of the femoral nerve,....Fig. 5.Semidiagrammatic ventral views of the femoral nerve, showing the distribution of the branches. × 3. 1,2, M. extensor iliotibialis anticus; 3, cutaneous; 5,6, M. extensor iliotibialis lateralis; 7,8, M. iliacus; 9, M. gluteus profundus; 10,11, fused Mm. vastus lateralis and vastus medialis; 13, M. vastus medialis; 15, M. ambiens; 16, M. femoritibialis internus; 17, nonmuscular; 18, M. psoas; 19, M. iliotrochantericus medius. A.Tympanuchus pallidicinctus2L. B.Tympanuchus cupido attwateri1R.
Fig. 6. Semidiagrammatic dorsolateral view of the sciatic nerve of...Fig. 6.Semidiagrammatic dorsolateral view of the sciatic nerve ofPedioecetes phasianellus jamesi3R, showing the distribution of the branches. × 2½. 1, M. gluteus profundus; 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4-7, M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; 13-15, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor ischiofemoralis; 18,19, M. femorocruralis (branch of tibial nerve); 20, cutaneous; 21, M. gastrocnemius pars media (branch of tibial nerve); 22, cutaneous.
Fig. 7. Semidiagrammatic dorsolateral view of the sciatic nerve of...Fig. 7.Semidiagrammatic dorsolateral view of the sciatic nerve ofTympanuchus pallidicinctus2L, showing the distribution of the branches. × 2½. 1, M. gluteus profundus; 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4, 7, M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; 13-15, M. caudofemoralis pars iliofemoralis; 17, M. flexor ischiofemoralis; 18, M. femorocruralis (branch of tibial nerve); 22, cutaneous; 23, nonmuscular (branch of peroneal nerve).
Fig. 8. Semidiagrammatic dorsolateral view of the sciatic nerve of...Fig. 8.Semidiagrammatic dorsolateral view of the sciatic nerve ofTympanuchus cupido pinnatus3L, showing the distribution of the branches. × 2½. 1, M. gluteus profundus; 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4,7, M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, cutaneous; 11, M. flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; 13, M. caudofemoralis pars iliofemoralis; 17, M. flexor ischiofemoralis; 18, M. femorocruralis (branch of tibial nerve); 20, cutaneous; 22, cutaneous.
Fig. 9. Semidiagrammatic dorsolateral view of the sciatic nerve of...Fig. 9.Semidiagrammatic dorsolateral view of the sciatic nerve ofPedioecetes phasianellus jamesi3L, showing the distribution of the branches. × 2½. 1, M. gluteus profundus; 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4,5,7, M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, cutaneous; 11, M. flexor cruris lateralis; 13,14, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor ischiofemoralis; 18,19, M. femorocruralis (branch of tibial nerve); 20, cutaneous; 22, cutaneous.
Fig. 10. Semidiagrammatic drawings of the peroneal nerve of...Fig. 10.A,B. Semidiagrammatic drawings of the peroneal nerve ofTympanuchus pallidicinctus1L, showing the distribution of the branches. × 2. C. Semidiagrammatic drawing of the distal part of the peroneal nerve ofTympanuchus cupido attwateri1R, showing the distribution of the branches. × 2. 1,2, M. tibialis anticus (tibial head); 3,4, M. tibialis anticus (femoral head); 5, M. extensor digitorum longus; 6, nonmuscular; 7,8, M. peroneus longus; 9, M. peroneus brevis; 10,11, M. extensor hallucis longus (proximal head); 12, M. extensor hallucis longus (distal head); 13-15, nonmuscular (to toes); 16, M. abductor digiti II; 17, M. extensor brevis digiti III; 18, M. extensor brevis digiti IV.
Fig. 11. Semidiagrammatic drawings of the tibial nerve (excluding...Fig. 11.A,B. Semidiagrammatic drawings of the tibial nerve (excluding the paraperoneal branch) ofTympanuchus pallidicinctus, showing the distribution of the branches. × 2. A. T.p. 1L. B. T.p. 3R. C. Semidiagrammatic drawing of the distal part of the paraperoneal branch of the tibial nerve ofPedioecetes phasianellus jamesi2L, showing the distribution of the branches. × 2. 1, M. femorocruralis; 2, M. gastrocnemius pars media; 3, M. popliteus; 4, M. plantaris; 5, M. flexor digitorum longus; 6-8, nonmuscular; 9-11, M. gastrocnemius pars interna; 12,13, M. flexor hallucis longus; 14-16, M. flexor perforatus digiti IV (medial head); 17, M. flexor perforatus digiti III (medial head); 18-20, M. flexor perforatus digiti II; 21, M. flexor perforatus digiti IV (lateral head); 22-24, M. flexor perforatus digiti IV (anterolateral head); 25, M. flexor perforatus digiti III (anterolateral head); 26, M. flexor perforans et perforatus digiti III; 27,28, M. flexor perforans et perforatus digiti II; 29, M. gastrocnemius pars externa; 30,31, M. abductor digiti IV; 32,33, M. flexor hallucis brevis; 34,35, nonmuscular (to toes).
In the accounts of the muscles the name used by Hudson,et al.(1959) for each muscle is given in parentheses after the name used by me if the two differ.
In the account of each muscle, the description of the condition found in most specimens of the Lesser Prairie Chicken (T. pallidicinctus) is given first. This is hereafter referred to as the typical condition forT. pallidicinctus. Then any individual variations found within this species are given. Under the headingT. cupidoany constant differences between this species and typicalT. pallidicinctusare given first, and any individual variations found within the speciesT. cupido(both subspecies considered together) are given second. Under the headingP. p. jamesiany constant differences between this subspecies and the typical condition forT. pallidicinctus(thus these differences are not necessarily constant between the two genera) are given first, and any individual variations found within the subspeciesP. p. jamesiare given second.
In the bird embryo, according to the studies of Romer (1927) and Wortham (1948), the muscles within each segment of the leg differentiate from distinct dorsal or ventral mesenchymal masses. Presumably these represent the primitive dorsal extensor and ventral flexor muscle masses. The list below indicates the ontogenetic origin of the avian leg muscles, according to the studies of Romer and Wortham. The individual muscles are discussed in the order in which they are listed below.
Dorsal muscles of thigh
Ventral muscles of thigh
Ventral muscles of shank
Dorsal muscles of shank
Dorsal muscles of foot
Ventral muscles of foot
Fig. 12. Tympanuchus pallidicinctus 2L. Lateral view of the superficial muscles of the left leg.Fig. 12.Tympanuchus pallidicinctus2L. Lateral view of the superficial muscles of the left leg. × 1.
M. Extensor Iliotibialis Lateralis(M. iliotibialis),Figs. 12,13,20F, G
T. pallidicinctus
Fig. 13. Tympanuchus pallidicinctus 2L. Medial view of the superficial muscles of the left leg.Fig. 13.Tympanuchus pallidicinctus2L. Medial view of the superficial muscles of the left leg. × 1. Articular capsule shown by concentrically arranged dashes.
General Description and Relations.—Most superficial muscle on lateral surface of thigh; broad, flat, and triangular; bounded anteriorly by M. extensor iliotibialis anticus and posteriorly by M. flexor cruris lateralis; posterior part considerably thicker than anterior part; anteroproximal and centrodistal parts aponeurotic; extreme posteroproximal corner also aponeurotic (could be considered tough sheet of connective tissue intimately fused with M. extensor iliotibialis lateralis, rather than part of muscle itself; seeFig. 20F); latter aponeurosis, as well as adjacent fleshy fibers, overlapped by M. flexor cruris lateralis; this aponeurosis fused with posterior end of underlying M. caudofemoralis pars iliofemoralis; centrodistal aponeurosis tightly fused to underlying Mm. vastus lateralis and vastus medialis; fleshy fibers posterior to this aponeurosis also fused with M. vastus lateralis, although posterior third ofmuscle free; fleshy part anterior to this aponeurosis bound by tough connective tissue to underlying M. vastus medialis, although no fusion of fibers; anterior edge tightly bound by strong connective tissue to M. extensor iliotibialis anticus, with some fusion of fibers (proximally); posteroproximal corner bound by tough connective tissue to adjacent muscles; anteroproximal aponeurosis fused with aponeurotic anteroproximal part of underlying M. extensor iliofibularis. Continuous proximal aponeurosis of M. extensor iliotibialis anticus and of M. extensor iliotibialis lateralis underlain by tough fascial sheet overlying M. gluteus profundus; anterior part of this fascia tightly fused to latter muscle but free from overlying aponeurosis; posterior part of this fascia tightly fused to overlying aponeurosis but free from M. gluteus profundus; middle part of fascia fused to both aponeurosis and M. gluteus profundus.
Fig. 14. Tympanuchus pallidicinctus 2L. Lateral view of the muscles of the left leg.Fig. 14.Tympanuchus pallidicinctus2L. Lateral view of the muscles of the left leg. The following muscles have been removed: extensor iliotibialis lateralis, extensor iliotibialis anticus, gastrocnemius pars externa and pars interna, and peroneus longus. × 1.
Fig. 15. Tympanuchus pallidicinctus 2L. Medial view of the muscles of the left leg.Fig. 15.Tympanuchus pallidicinctus2L. Medial view of the muscles of the left leg. The following muscles have been removed: extensor iliotibialis lateralis, extensor iliotibialis anticus, ambiens, flexor cruris lateralis (in part), flexor cruris medialis (in part), gastrocnemius pars externa and pars interna, and peroneus longus. × 1.
Origin.—Approximately the anterior half attaches by an extensive aponeurosis, which is continuous anteriorly with that of M. extensor iliotibialis anticus, to the anterior iliac crest, ending posteriorly at the anterior end of the lateral iliac process; the posterior part attaches fleshily to the edge of the entire lateral iliac process and (posterior few mm.) aponeurotically to the entire lateral ischiatic ridge. The proximal part of the belly is much thicker than the fleshy origin. Two accessory aponeuroses associate with the anterior part of the muscle; the proximal one of these comes off the deep surface several mm. distal to the proximal end of the fleshy belly and passes medially between Mm. gluteus profundus and iliacus, fusing to both these muscles, and attaches to the lateral edge of M. iliotrochantericus medius and to the lateral edge of the ilium anterior to the latter; the aponeurosis actually splits into two sheets at the edge of M. iliotrochantericus medius; these sheets fuse to the dorsal and ventral surfaces of the latter muscle, enclosing it; the part of this aponeurosis between Mm. iliacus and iliotrochantericus medius is strongly fused with the underlying body wall. The distal accessory aponeurosis(sometimes weak) comes off the deep surface several mm. distal to the proximal one and passes medially along the ventral surface of M. iliacus, fusing with the latter, then joining the proximal accessory aponeurosis medial to M. iliacus.
Insertion.—The muscle inserts by a broad aponeurosis strongly fused to the underlying Mm. vastus lateralis and vastus medialis; the aponeurosis contributes superficially to the patellar tendon, attaching to the lateral half of the rotular crest.
Fig. 16. Tympanuchus pallidicinctus 2L. Lateral view of the muscles of the left leg.Fig. 16.Tympanuchus pallidicinctus2L. Lateral view of the muscles of the left leg. The following muscles, in addition to those listed forFig. 14, have been removed: ambiens, vastus lateralis pars lateralis, vastus medialis (except for part of patellar tendon), extensor iliofibularis, flexor cruris lateralis (in part), flexor perforans et perforatus digiti II, and flexor perforans et perforatus digiti III. × 1.
Innervation.—A variable number of branches (usually two) of the middle division of the femoral nerve pass ventral to M. iliacus and between Mm. extensor iliotibialis anticus and vastus medialis and enter the deep surface of the anteroproximal part of the muscle. The branch of the middle peronealdivision of the sciatic nerve emerges between the proximal ends of Mm. extensor iliofibularis and vastus lateralis and sends twigs into the deep surface of M. extensor iliotibialis lateralis.
Individual Variation.—In two legs, the nerve supplying M. extensor iliotibialis anticus gives twigs into M. extensor iliotibialis lateralis.
T. cupido
Differences FromT. pallidicinctus.—The fleshy origin from the lateral iliac process is considerably thicker (reflected in a thicker lateral iliac process).
Individual Variation.—In three legs the nerve supplying M. extensor iliotibialis anticus gives twigs into M. extensor iliotibialis lateralis. In another leg one of the branches to the fused Mm. vastus lateralis and vastus medialis sends a twig into M. extensor iliotibialis lateralis.
Fig. 17. Tympanuchus pallidicinctus 2L. Lateral view of the muscles of the left leg.Fig. 17.Tympanuchus pallidicinctus2L. Lateral view of the muscles of the left leg. The following muscles, in addition to those listed forFig. 16, have been removed: vastus lateralis pars postica, gluteus profundus, flexor cruris medialis (in part), caudofemoralis, flexor perforatus digiti IV, and tibialis anticus. × 1.
P. p. jamesi
Fig. 18. Tympanuchus pallidicinctus 2L. Lateral view of the muscles of the left leg.Fig. 18.Tympanuchus pallidicinctus2L. Lateral view of the muscles of the left leg. The following muscles, in addition to those listed forFig. 17, have been removed: patellar tendon, iliacus, iliotrochantericus medius, flexor cruris lateralis, flexor cruris medialis, flexor ischiofemoralis, adductor superficialis, femorocruralis, gastrocnemius pars media, flexor perforatus digiti III, flexor perforatus digiti II, flexor hallucis longus, plantaris, flexor digitorum longus, popliteus, and extensor digitorum longus. × 1.
Differences From TypicalT. pallidicinctus.—The posteroproximal aponeurosis is more extensive, resulting in a narrower proximal fleshy end (Fig. 20G); the fleshy fibers adjacent to this aponeurosis are not overlapped by M. flexor cruris lateralis. There is a fusion of fibers between the anterodistal fleshy part of M. extensor iliotibialis lateralis and the underlying M. vastus medialis, but there is no fusion of fibers between the anterior edge of M. extensor iliotibialis lateralis and M. extensor iliotibialis anticus. The connective tissue binding the posteroproximal corner to adjacent muscles is stronger. The fleshy part of the origin is narrower, partly tendinous, and much thinner (reflected in a thin lateral iliac process). The proximal border is much more nearly straight, owing to a less pronounced lateral iliac process. The distal accessory aponeurosis is absent.
Fig. 19. Tympanuchus pallidicinctus 2L. A. Posterior view of the muscles of the left shank. The following shank...Fig. 19.Tympanuchus pallidicinctus2L. A. Posterior view of the muscles of the left shank. The following shank muscles, in addition to those listed forFig. 17, have been removed: gastrocnemius pars media, flexor perforatus digiti III, and flexor perforatus digiti II. × 1. B. Posterior view of the proximal end of the shank, showing the most deeply situated muscle. × 1. C. Lateral view of the head of the left femur and the middle part of the pelvis, showing the deepest part of M. obturator. × 1. D. Medial view of the posteroventral part of the left side of the pelvis, showing the intrapelvic part of M. obturator. × 1. E. Anterior view of the left tarsometatarsus, showing the dorsal intrinsic muscles of the foot. × 1½. F. Posterior view of the left tarsometatarsus, showing the ventral intrinsic muscles of the foot. × 1½.
Individual Variation.—The muscle is usually somewhat fused to the posteroproximal and anteroproximal fleshy corners of the underlying M. extensor iliofibularis.
M. Extensor Iliotibialis Anticus(M. sartorius),Figs. 12,13
T. pallidicinctus
General Description and Relations.—Anteriormost muscle of thigh; long and strap-shaped; proximal part entirely anterior (adjacent) to M. extensor iliotibialis lateralis; posterior edge of middle part medial to latter muscle; distal part mostly medial to Mm. extensor iliotibialis lateralis and vastus medialis; proximal part aponeurotic, continuous posteriorly with anteroproximal aponeurosis of M. extensor iliotibialis lateralis; anterior edge of M. extensor iliotibialis lateralis bound by strong connective tissue to adjacent part of M. extensor iliotibialis anticus; some fusion of fibers (proximally) between these two muscles; anteroproximal corner of fleshy part of muscle sometimes fused to underlying anterior edge of ilium and fascia covering body wall musculature adjacent (anterior) to ilium.
Origin.—The muscle arises aponeurotically from the anterior part of the anterior iliac crest and (anteroproximal corner) from the anterior end of the median dorsal ridge.
Insertion.—The flat tendon, continuous posteriorly with the superficial tendon of M. femoritibialis internus, fuses to the tendon of M. vastus medialis, contributing superficially to the medial part of the patellar tendon, which attaches to the medial half of the rotular crest; most of the tendon is overlapped by the edge of M. gastrocnemius pars interna.
Innervation.—A branch of the anterior division of the femoral nerve gives twigs into the lateral surface of the posterior part.
Individual Variation.—In two legs, a twig from the anteriormost branch of the middle division of the femoral nerve anastomoses with the typical branch to M. extensor iliotibialis anticus.
T. cupido
Individual Variation.—In several legs, the anterior edge of origin extends forward onto the neural spine of the last free thoracic vertebra. A twig from the middle division of the femoral nerve anastomoses with the typical branch to M. extensor iliotibialis anticus in three legs.
P. p. jamesi
Differences From TypicalT. pallidicinctus.—There is no fusion of fibers between M. extensor iliotibialis anticus and M. extensor iliotibialis lateralis.
Individual Variation.—The anterior edge of origin extends forward onto the neural spine of the last free thoracic vertebra in some legs.
Fig. 20. Dorsal views of M. iliotrochantericus medius, ...Fig. 20.A-D. Dorsal views of M. iliotrochantericus medius, showing its relationship to femoral notch. × 1. In D, note absence of femoral notch and location of branch of femoral nerve. A.Tympanuchus pallidicinctus2L. B.T. cupido pinnatus4L. C.Pedioecetes phasianellus jamesi1L. D.T. pallidicinctus3L.E. Medial view of distal end of M. flexor cruris medialis ofP. p. jamesi4L. × 1. Part of insertion is covered by medial collateral ligament.F,G. Lateral views of posteroproximal corner of M. extensor iliotibialis lateralis (removed from specimen). × 1. F.T. pallidicinctus2L. G.P. p. jamesi3L.H,I. Dorsolateral views of M. piriformis. × 1. H.P. p. jamesi1L. I.T. cupido attwateri1L.J. Lateral view of M. caudofemoralis pars caudifemoralis (removed from specimen) ofT. c. pinnatus4L. × 1. K. Lateral view of extrapelvic part of M. obturator ofT. pallidicinctus3L (bones not shown). × 2.L,M. Region surrounding obturator foramen ofT. pallidicinctus3L, showing points of attachment of three parts of M. obturator (muscles removed). × 3. L. Lateral view. M. Medial view.N. Anterior view of left tarsometatarsus ofP. p. jamesi4L, showing dorsal intrinsic muscles of foot. × 1½. Tendon of M. extensor digitorum longus has been removed.
M. Ambiens,Figs. 13,16,17
T. pallidicinctus
General Description and Relations.—Thin and elongate; on medial surface of thigh; broadest above middle of belly; belly narrowed distally, forming long slender tendon passing lateral to distal part of M. extensor iliotibialis anticus; bounded anterolaterally by M. vastus medialis and posterolaterally by Mm. femoritibialis internus and psoas (proximally).
Origin.—The muscle arises by a short flat tendon from the pectineal process.
Insertion.—The long slender tendon enters an elongate channel within the patellar tendon; the point of entrance is at the proximal end of the latter tendon just medial to the patella; the tendon passes distolaterally (within the channel) below the patella and emerges from the distolateral edge of the patellar tendon and then extends distally along the anterolateral surface of the head of the fibula, superficial to the fibular arm of the guide loop for M. extensor iliofibularis, and joins the anterolateral surface of the common tendon of origin of the anterolateral heads of Mm. flexor perforatus digiti III, flexor perforatus digiti IV, and flexor perforatus digiti II; the point of junction is usually immediately proximal to the proximal end of the lateral head of M. flexor digitorum longus.
Innervation.—The branch of the middle division of the femoral nerve that supplies M. femoritibialis internus gives off a tiny twig or twigs that penetrate the lateral surface of the proximal part of M. ambiens.
Individual Variation.—None of significance inT. pallidicinctusor inP. p. jamesi; inT. cupidothe origin is partly fleshy in one leg.
M. Vastus Lateralis(M. femoritibialis externus + part of M. femoritibialis medius),Figs. 14,16
Fisher and Goodman (1955) apply the name femoritibialis externus to the muscle unit that I here term the pars postica of M. vastus lateralis. The reasons for this change are discussed in the section on terminology.
T. pallidicinctus
General Description and Relations.—Thick; on lateral surface of femur deep to M. extensor iliotibialis lateralis; anterior to M. extensor iliofibularis and lateral to M. vastus medialis; much of lateral surface, except proximal part, fused with overlying M. extensor iliotibialis lateralis; deep surface of anterior half fused with M. vastus medialis; proximal part overlapping, but usually not fusing with, insertions of Mm. iliacus and caudofemoralis; partially separable into two parts—pars lateralis and pars postica, former constituting main part of muscle; latter considerably smaller and situated deep to posterodistal part of pars lateralis, except for posterodistal part extending posterior to edge of pars lateralis; proximal part of pars postica strongly fused with pars lateralis; posterodistal tendinous edge of pars lateralis fused or not fused with lateral surface of pars postica; proximal end (narrow) of pars postica tendinous and variable in length.
Origin.—Pars lateralis: This arises fleshily from most of the lateral surface and (distally) from the anterior surface of the femur, extending anteriorly tothe anterior intermuscular line, fusing with M. vastus medialis, and extending posteriorly to the posterolateral intermuscular line (proximally) and the origin of pars postica (distally); the proximal end begins at the level of the distal edge of the insertion of M. iliotrochantericus medius, contacting the insertions of Mm. iliotrochantericus medius, piriformis, and flexor ischiofemoralis, and terminates distally at the level of the proximal ends of the femoral condyles.
Pars postica: This arises fleshily and tendinously (proximal end and deep surface) from the posterolateral surface of approximately the distal half of the femur, extends posteromedially to the posterolateral intermuscular line where it contacts the origin of M. femorocruralis, and extends anteriorly to the level of a line drawn diagonally across the femur from the proximal end of the origin (at the posterolateral intermuscular line) to the proximal end of the external condyle; the distal end is anterior (adjacent) to the attachment of the proximal arm of the tendinous guide loop for M. extensor iliofibularis; the origin is adjacent to, but distinct from, the origin of pars lateralis.
Insertion.—Pars lateralisis fused indistinguishably with M. vastus medialis; these two muscles form the main (middle) part of the patellar tendon, which also receives contributions from pars postica and Mm. femoritibialis internus, extensor iliotibialis lateralis, and extensor iliotibialis anticus; the patellar tendon attaches to the entire rotular crest of the tibia; the patella is situated in the proximal part of this tendon; some deep fleshy fibers of M. vastus lateralis pars lateralis and M. vastus medialis attach to the proximal edge of the patella.Pars posticaforms a short narrow tendon that fuses to the lateral part of the tendon of pars lateralis, forming the lateralmost part of the patellar tendon. A broad flat vinculum extends from the lateral surface of the femorofibular fascia (defined under M. flexor perforans et perforatus digiti II) to the deep surface of the lateral part of the patellar tendon; a similar vinculum extends from the medial surface of the internal condyle to the deep surface of the medial part of the patellar tendon.
Innervation.—Two or more branches of the middle division of the femoral nerve penetrate the anterior surface of the fused Mm. vastus lateralis (pars lateralis) and vastus medialis; short twigs emerge from the deep surface of pars lateralis and penetrate the superficial surface of the anteroproximal part of pars postica.
Individual Variation.—The proximal ends of M. vastus medialis and M. vastus lateralis are usually separated by a deep notch. In some legs, a small bundle of fibers forming the anteroproximal part of M. vastus lateralis attaches to the lateral surface of M. vastus medialis anterior to this notch.
T. cupido
Individual Variation.—One leg shows the same variation found inT. pallidicinctus(see above). In several legs, pars lateralis does not extend so far proximally as usual, but begins at the level of insertion of M. piriformis (does not contact the insertion of M. iliotrochantericus medius) and may not overlap M. iliacus. In a few legs, no vincula are associated with the patellar tendon.
P. p. jamesi
Individual Variation.—Pars lateralis often begins proximally at the level of the insertion of M. piriformis.
M. Vastus Medialis(Part of M. femoritibialis medius),Figs. 13,14,15
T. pallidicinctus
General Description and Relations.—Thick; on anteromedial surface of femur medial to anterior part of M. vastus lateralis pars lateralis; bounded medially by Mm. ambiens and extensor iliotibialis anticus (distally); bounded posteromedially by M. femoritibialis internus; proximal part medial to posterior ends of Mm. iliacus, iliotrochantericus medius, and gluteus profundus; lateral surface, except proximal part, fused with anterior part of M. vastus lateralis pars lateralis; part of lateral surface of M. vastus medialis covered by sheet of fascia attaching to anterior intermuscular line; M. vastus lateralis separable from this fascia, but fascia absent anteriorly and distally and these two muscles indistinguishably fused.
Origin.—The proximal third is attached narrowly by its lateral edge; the distal two thirds is attached broadly by its entire deep surface. The proximal third arises tendinously from the trochanteric ridge and the proximal end of the anterior intermuscular line and fleshily from a narrow area of the femur adjacent (medial) to the latter; the distal part arises tendinously from the anterior intermuscular line and fleshily from a broad adjacent area on the anteromedial surface of the femur, terminating distally at the level of the proximal end of the internal condyle; the posterior edge contacts the origin of M. femoritibialis internus.
Insertion.—Attachment is in common with M. vastus lateralis pars lateralis, which see.
Innervation.—Two or more branches of the middle division of the femoral nerve penetrate the anterior surface of the fused Mm. vastus medialis and vastus lateralis pars lateralis; a variable number of branches of the same division penetrate the medial surface of the proximal part of M. vastus medialis.
Individual Variation.—None of significance in any of the three species studied.
M. Femoritibialis Internus,Figs. 13,15
T. pallidicinctus
General Description and Relations.—Elongate; on posteromedial surface of femur; bounded anteriorly by M. vastus medialis and posteriorly by M. adductor profundus (overlapping anterior edge of latter); anteroproximal part lateral to M. ambiens; anterodistal corner deep to distal end of M. extensor iliotibialis anticus; distal part of muscle split into superficial and deep layers; superficial layer thin, narrow, and tendinous except for proximal end; deep layer wider, much thicker, and fleshy except for distal end taking form of flat tendon; anterior edge of latter somewhat fused to medial edge of tendon of M. vastus medialis; deep layer widest near distal end of fleshy part; posterior edge of superficial layer fused to underlying deep layer, and anterior edge fused to (continuous with) posterior edge of tendon of M. extensor iliotibialis anticus.
Origin.—The origin is mostly fleshy from the posteromedial surface of the femur between the origin of M. vastus medialis and the posterior intermuscular line, terminating immediately proximal to the internal condyle.
Insertion.—The tendons of both superficial and deep layers attach to the medial part of the rotular crest, forming the medialmost part of the patellar tendon.
Innervation.—The posteriormost branch of the middle division of the femoral nerve penetrates the medial surface of the muscle near the proximal end.
Individual Variation.—None of significance in any of the three species studied.
M. Extensor Iliofibularis(M. biceps femoris),Figs. 12,14,16,17
The term extensor in the name of this muscle does not refer to its function. Howell (1938) used the term extensor to indicate derivation of the muscle from the primitive dorsal extensor muscle mass. (Likewise he used the term flexor to indicate derivation from the primitive ventral flexor muscle mass.)
T. pallidicinctus
General Description and Relations.—Deep to M. extensor iliotibialis lateralis and posterior to femur; broad proximally and narrow distally; posterior to M. vastus lateralis and anterior to proximal part of M. flexor cruris lateralis (superficial to distal part of latter); anteroproximal part aponeurotic, fused to deep surface of aponeurosis of M. extensor iliotibialis lateralis; proximal part of aponeurosis of M. extensor iliofibularis also fused to dorsal edges of underlying Mm. gluteus profundus and piriformis.
Origin.—The posterior part is fleshy from the ventromedial surface of the entire lateral iliac process; the anterior part is aponeurotic from the posterior part of the anterior iliac crest.
Insertion.—The tendon forms along the posterodistal edge of the belly and continues beyond the end of the belly as a cylindrical tendon that passes through the tendinous guide loop (the belly terminates approximately at the level of the guide loop), then extends anterodistally into the shank musculature; the tendon passes between the medial and lateral heads of M. flexor perforatus digiti IV, between the medial and lateral heads of M. flexor perforatus digiti II, lateral to the common tendon of the anterolateral heads of Mm. flexor perforatus digiti IV, flexor perforatus digiti II, and flexor perforatus digiti III, and between the posterior and lateral heads of M. flexor digitorum longus, attaching to the fibular tubercle.
The tendinous guide loop has three arms—proximal femoral, distal femoral, and fibular; the proximal and distal femoral arms unite posterior to the tendon of M. extensor iliofibularis; the proximal arm is medial to, and the distal arm is lateral to, the latter; the fibular arm joins the distal edge of the distal arm lateral to the tendon of M. extensor iliofibularis. The proximal arm extends anteroproximally lateral to the medial head of M. flexor perforatus digiti IV and medial to M. vastus lateralis pars postica, attaching to a narrow line on the anterolateral surface of the femur a short distance proximal to the external condyle and adjacent (posterior) to the origin of M. vastus lateralis pars postica. The distal arm extends anteriorly medial to the posterior head of M. flexor perforans et perforatus digiti II and medial to M. vastus lateralis pars postica, attaching in common with the tendon of origin of M. gastrocnemius pars externa to a small oval area on the posterolateral surfaceof the femur a short distance proximal to the fibular groove; the arm is also fused to the underlying articular capsule. The fibular arm (broadest of the three) passes deep to, and fused with, the common tendon of origin of the lateral heads of Mm. flexor perforatus digiti IV and flexor perforatus digiti II, superficial to the common tendon of origin of the anterolateral heads of Mm. flexor perforatus digiti IV, flexor perforatus digiti II, and flexor perforatus digiti III, and deep to the tendon of M. ambiens, attaching broadly to a narrow line on the anterolateral surface of the proximal part of the fibula; the arm is also fused to the underlying articular capsule.
Innervation.—A branch of the middle peroneal division of the sciatic nerve sends twigs to the deep surface of the anteroproximal part; the dorsal peroneal division of the sciatic nerve penetrates the deep surface of the proximal end.
Individual Variation.—In some instances a variable number of twigs arises from the peroneal nerve near the middle of the thigh and enters the deep surface of the muscle. They are difficult to expose without breaking and may have been overlooked in some specimens.
T. cupido
Individual Variation.—The same variation is found as inT. pallidicinctus(see above). In one leg, the tendon of insertion bifurcates into proximal and distal arms before attaching.
P. p. jamesi
Differences from TypicalT. pallidicinctus.—It arises from the ventral rather than the ventromedial surface of the lateral iliac process (there is no ventromedial surface to this process).
Individual Variation.—In nearly all of the legs, minute twigs to M. extensor iliofibularis come off the peroneal nerve near the middle of the thigh. The insertional tendon tends toward doubleness in two legs.
M. Piriformis(M. gluteus medius et minimus),Figs. 16,20H, I
T. pallidicinctus
General Description and Relations.—Small, thin, and triangular; lateral to antitrochanter and posterior part of trochanter; deep to M. extensor iliofibularis and posterior (adjacent) to M. gluteus profundus; distal half (or more) tendinous.
Origin.—The muscle arises fleshily from the posterior end of the anterior iliac crest (ventral to the origins of Mm. extensor iliotibialis lateralis and extensor iliofibularis) beginning adjacent to the posterior end of M. gluteus profundus.
Insertion.—The flat tendon narrows, overlaps the anteroproximal corner of insertion of M. flexor ischiofemoralis, and attaches to the lateral surface of the proximal part of the femur immediately anterior to the insertion of M. flexor ischiofemoralis and posterior to the proximal end of M. vastus lateralis; the attachment is posterodistal to the insertion of M. iliotrochantericus medius and posteroproximal to the insertion of M. iliacus.
Innervation.—The small anterior peroneal division of the sciatic nerve turns anteriorly immediately after emerging from the ilio-ischiatic fenestra and passes deep to M. piriformis, giving twigs to the deep surface.
Individual Variation.—In both legs of one specimen, the insertion does not overlap the insertion of M. flexor ischiofemoralis. The posteroproximal corner of the muscle is tendinous in one leg.
T. cupido
Individual Variation.—The anterior border is somewhat fused with the posterior edge of M. gluteus profundus in one leg, while in another there is a slight gap between the origins of M. gluteus profundus and M. piriformis. In one leg, the posterior edge of the origin is aponeurotic. On both sides of one specimen, an accessory tendinous band arises several mm. posterior to the main part of M. piriformis and joins the proximal part of the insertional tendon, thus forming a Y-shaped unit (Fig. 20I); the accessory tendon arises from the anterior end of the lateral iliac process (left side) or from the anterior part of the lateral iliac fossa (right side). The insertion may be proximal (rather than posterior) to the proximal end of M. vastus lateralis. In one leg, the insertional tendon is partly fused to the insertional tendon of M. flexor ischiofemoralis.
P. p. jamesi
Individual Variation.—There is often a gap between the origins of M. gluteus profundus and M. piriformis. In one leg (Fig. 20H), the posteroproximal corner of the muscle is aponeurotic. The insertion is often proximal (rather than posterior) to the proximal end of M. vastus lateralis. In one instance, the insertion does not overlap the insertion of M. flexor ischiofemoralis.
M. Gluteus Profundus(M. iliotrochantericus posterior),Figs. 14,16
T. pallidicinctus
General Description and Relations.—Large and thick; covering dorsolateral surface of entire preacetabular part of ilium; deep to Mm. extensor iliotibialis lateralis and extensor iliotibialis anticus; bounded posteriorly by M. piriformis and ventrally by M. iliacus; ventral edge fused with anterior part of latter and with proximal accessory aponeurosis of M. extensor iliotibialis lateralis; tough sheet of fascia strongly fused to anterior two thirds of lateral surface; posterior to this, fascia overlying muscle but not attaching to it; posterior half of fascia fused to overlying aponeurosis of M. extensor iliotibialis lateralis; deep surface of muscle somewhat fused to proximal part of M. iliotrochantericus medius.
Origin.—The superficial surface is tendinous from the entire anterior iliac crest except the posterior end and from the crest forming the anterior and anterolateral edges of the ilium; the muscle arises fleshily from the entire dorsolateral surface of the preacetabular ilium as far posteriorly as the level of the pectineal process; the dorsal edge is adjacent (anterior) to the origin of M. piriformis.
Insertion.—The attachment is by a short, wide, thick tendon to a curved line (convex anteriorly) on the lateral surface of the femoral trochanter.
Innervation.—The anterodorsal division of the femoral nerve turns dorsallythrough the femoral notch of the ilium and penetrates the deep surface of the ventral part of the muscle midway of its length; the anterior peroneal division of the sciatic nerve passes deep to M. piriformis and terminates near the posterodorsal edge of M. gluteus profundus.
Individual Variation.—On both sides of one specimen, the branch from the femoral nerve passes lateral to the extreme anteroproximal corner of M. iliotrochantericus medius instead of through the femoral notch.
T. cupido
Individual Variation.—In one leg, the insertional tendon is strongly fused to the insertional tendon of M. iliotrochantericus medius.
P. p. jamesi
Individual Variation.—None of significance.
M. Iliacus(M. iliotrochantericus anterior),Figs. 13,14,15,16,17
T. pallidicinctus
General Description and Relations.—Adjacent ventrally to ventrolateral edge of M. gluteus profundus; lateral edge much thicker than medial edge; deep to M. extensor iliotibialis lateralis and anterolateral to M. iliotrochantericus medius; distal (posterior) end passing between proximal ends of Mm. vastus medialis and vastus lateralis pars lateralis; insertion overlapped by latter; dorsal surface of anterior part fused with ventrolateral edge of M. gluteus profundus and with ventral surface of proximal accessory aponeurosis of M. extensor iliotibialis lateralis; ventral surface partly fused with distal accessory aponeurosis of latter muscle.
Origin.—The origin is fleshy and tendinous from the lateral edge of the anterior part of the ilium.
Insertion.—The attachment is by a short flat tendon to the lateral surface of the femur distal to the trochanter and anterodistal to the insertion of M. piriformis and deep to the proximal part of M. vastus lateralis pars lateralis.
Innervation.—The dorsal division of the femoral nerve penetrates the ventral surface.
Individual Variation.—The dorsal division of the femoral nerve may fuse proximally with either the anterior or middle division. In one leg, there are two separate branches to the muscle.
T. cupido
Individual Variation.—The insertion may not be overlapped by M. vastus lateralis. The dorsal division of the femoral nerve is fused proximally with the middle division in one leg.
P. p. jamesi
Differences from TypicalT. pallidicinctus.—The fleshy origin is wider.
Individual Variation.—The dorsal division of the femoral nerve may fuse proximally with either the anterior or middle division. In one leg, there are two branches to M. iliacus, one fused with the anterior division and the other with the middle division.
M. Iliotrochantericus Medius,Figs. 17,20A, B, C, D
T. pallidicinctus
General Description and Relations.—Small and triangular; ventral to posterior half of M. gluteus profundus; all but posteroventral corner deep to latter; posteromedial to M. iliacus, anterior to neck of femur, and dorsolateral (adjacent proximally) to M. psoas; proximal end notched at level of femoral notch for passage of anterodorsal division of femoral nerve; part anterior to femoral notch mainly tendinous; dorsal surface of proximal part somewhat fused to M. gluteus profundus, proximal accessory aponeurosis of M. extensor iliotibialis lateralis split into two sheets enclosing and fusing with M. iliotrochantericus medius, ultimately attaching to lateral edge of ilium in common with origin of latter muscle.
Origin.—The muscle arises from the ventrolateral surface of the ilium anterior to the acetabulum and posterior to the origin of M. iliacus; the anterior part attaches to the ventrolateral edge of the ilium and the posterior part attaches just above the ventral edge. The muscle is not attached to the concavity of the femoral notch (the origin is notched here). The part attaching anterior to the femoral notch is narrow, tendinous, and continuous anteriorly with the accessory aponeurosis of M. extensor iliotibialis lateralis (thus the anterior border of the muscle cannot be exactly delimited). The part attaching posterior to the femoral notch is wider and fleshy (Fig. 20A).
Insertion.—The short flat tendon attaches to the lateral surface of the distal end of the trochanter slightly anterior and immediately distal to the insertion of M. gluteus profundus; the attachment is proximal to the origin of M. vastus lateralis, anteroproximal to the insertion of M. piriformis, and several mm. proximal to the insertion of M. iliacus.
Innervation.—The small posterodorsal division of the femoral nerve penetrates the ventral surface.
Individual Variation.—On both sides of one specimen, the femoral notch is absent and the proximal end of the muscle is not notched; the proximal part is entirely fleshy and the anterior border is well defined (Fig. 20D).
T. cupido
Individual Variation.—The part attaching anterior to the femoral notch has a fleshy origin in one leg (Fig. 20B), but in another, no part attaches anterior to the femoral notch (thus the muscle is not notched). In one leg, the insertional tendon is strongly fused to, and continuous with, the ventral edge of the insertional tendon of M. gluteus profundus.
P. p. jamesi
Individual Variation.—The part attaching anterior to the femoral notch may be mainly or entirely fleshy. In one leg, the part attaching anterior to the femoral notch is entirely separate from, although overlapped by, the main part of the muscle for the entire length of the fleshy belly (Fig. 20C); both parts have a common insertional tendon.
M. Psoas(M. iliacus),Figs. 13,15,18
T. pallidicinctus
General Description and Relations.—Small and slender; on medial aspect of proximal end of thigh lateral to proximal end of M. ambiens; ventromedial to M. iliotrochantericus medius; proximal end visible from inside pelvis (medial to inguinal ligament); passes dorsolateral to inguinal ligament.
Origin.—The muscle arises fleshily from the ventrolateral edge of the ilium posterior to the femoral notch and ventral (adjacent) to the origin of M. iliotrochantericus medius.
Insertion.—The attachment is tendinous to the medial surface of the femur a short distance proximal to the origin of M. femoritibialis internus.
Innervation.—The posterior division of the femoral nerve, which spirals completely around M. psoas, gives several twigs into the proximal part.
Individual Variation.—None of significance.
T. cupido
Individual Variation.—In two legs the insertion is partly fleshy.
P. p. jamesi
Individual Variation.—In one leg the insertion is partly fleshy. The posterior division of the femoral nerve perforates the muscle in one instance.
M. Flexor Cruris Lateralis(M. semitendinosus),Figs. 12,13,14,15,16,17