This is a broad and flat muscle, thinned out at either extremity; it occupies the inner half of the ventral surface of the thigh, and is in relation with the adductor magnus externally and anteriorly, with the sartorius posteriorly, and the rectus minor muscle internally. The muscle arises by a tendon from the pubic symphysis; it covers in its course the semitendinosus, then passes into a strong tendon, which blends with the tendon of the rectus minor, to be inserted by a slip into a process of the tibio-fibula representing the tuberositas tibiae; first passing between the tendons of the sartorius and semimembranosus, which here form an aponeurotic arch; a second slip passes under the tendon of the m. semitendinosus to be inserted into the upper surface of the tibio-fibula, under it passes the N. tibialis. A third thread-like tendon passes to the m. semimembranosus. Somewhat behind its middle (Fig. 82) the muscle is traversed by an inscriptio tendinea, by which the whole of the fibres are interrupted.

118. M. rectus internus minor (Ecker), (Figs. 80, 81 r.i″).

Situated entirely on the inner surface of the thigh, this narrow muscle arises by a tendinous band which runs the whole length of the pubic symphysis, and is connected posteriorly with the sphincter ani, anteriorly with the rectus abdominis; posteriorly it passes into a thin tendon which is also connected with the muscle just described (117). In its course this muscle is attached to the skin by strands of vessels and connective tissue.

The vastus internus major and minor together undoubtedly correspond with rectus internus or gracilis of human anatomy. The rectus internus major is, however, regarded as corresponding with the adductor magnus by Dugès, and with the semimembranosus by Klein; by considering the position and attachments of these muscles one must arrive at a different conclusion.

MM. adductores femoris.

119. [a] M. adductor longus (Fig. 82 ad′).

Without further dissection this muscle is only partially visible between the m. sartorius and vastus internus (Fig. 81 ad′). The muscle is flat and long, and arises by a tendon from the anterior inferior angle of the pubic symphysis (Fig. 42 s), partially covered by the origin of the sartorius. Thence the muscle passes between the vastus internus and the adductor magnus, and finally is inserted below the middle of the femur, together with the latter muscle.

120. [b] M. adductor magnus (Figs. 81, 82 ad‴).

This muscle is visible between the sartorius and rectus internus major in the anterior half of the thigh, posteriorly it is covered by these muscles. It arises by a tendon from (a) the pubic symphysis and ischii, and is in this position divided into two portions, between which passes the tendon of one head of the m. semitendinosus (Fig. 83 st″); (b) a second part arises from this same tendon (Fig. 83 st‴) and joins with the first part. Thus formed the muscle passes to be inserted into the distal half of the inner surface of the femur as far as the condyle. Near its hinder extremity, however, it passes on to the dorsal and outer surfaces, and thus forms a kind of muscular sheath surrounding the distal portion of the bone.

121. [c] M. adductor brevis (Figs. 81, 83 ad″),

and

122. [d] M. pectineus (Fig. 83 pe).

These two small muscles which lie under cover of the sartorius, adductor longus and magnus, appear externally as one muscle, but may easily be separated (Fig. 83). They arise close together from the pubic symphysis, and are inserted into the inner surface of the anterior half of the femur. They are not attached to the adductor magnus.

123. M. semitendinosus (Fig. 83 st, st′, st″).

This is a long thin muscle, only visible after removal of the m. rectus internus, by which it is entirely covered. It arises by two long thin tendons, one (caput posticum, st′) from the pubic symphysis, the other (caput anticum, st″) from the hollow between the symphysis and the acetabulum. The latter passes through a slit in the adductor magnus, and so affords this muscle another point of origin; then backwards between the adductor magnus and the rectus internus major and under the lower third of the thigh, and unites with the posterior head of origin. The muscle so formed passes into a thin tendon, and, together with that of the sartorius, forms an aponeurotic arch, connected with the fascia of the leg, under which the tendons of the rectus internus major and minor pass.

(C.) Deep muscles of the thigh.

To these, in addition to the adductor brevis, pectineus, and the portion of the biceps already described, belong also the following:

124. M. ilio-psoas (Figs. 82, 83, 84 ip).

The fibres of this muscle take a broad origin from the pelvic surface of the ilium, pass outwards over the lower margin of the bone and form a flat muscle with its apex pointed posteriorly. It crosses the hip-joint between the m. rectus and vastus internus, covering the hinder part of the m. glutaeus, and is inserted into the outer surface of the middle third of the femur.

125. M. quadratus femoris (Fig. 84 qf).

This muscle is of a somewhat elongated, triangular shape, and arises, under cover of the pyriformis, from the ilium behind the acetabulum; it passes backwards over the joint to be inserted into the inner and under surfaces of the femur, between the pyriformis and ilio-psoas; below, it is in direct relation with the adductor brevis.

126. M. obturatorius (Figs. 84, 85 og).

This small muscle is deeply situated upon the hip-joint, and covered by all the other muscles that arise from the symphysis. Its origin from the innominate bone extends from the superior posterior angle of the symph. ossis ilii to about the middle of the pubic symphysis; the muscle fills the space between the crest of the symphysis and the acetabulum. The fibres converge to pass into a strong tendon, which is inserted into the posterior and anterior surfaces of the head of the femur. The muscle appears to represent collectively the small rotators of human anatomy, m. obturator externus and internus and the gemelli.

II. Muscles of the Leg.

General description.

127. M. gastrocnemius (Figs. 80, 81, 86).

On the outer surface (the anterior of man), covered by the fascia cruris, into which the tendon of the extensor communis cruris or triceps is prolonged, are found the following muscles: nearest to the bone, the m. extensor cruris brevis (ec); externally, the m. tibialis anticus (ta) and the m. peroneus (pe). On the inner surface (the hinder of man) lie the gastrocnemius (gc) and tibialis posticus (tp), and deeply the flexor tarsi sup. (ft).

This important muscle arises by two tendinous heads. The one (Fig. 86 g′) rather nearer the middle line of the popliteal space, is by far the stronger: it arises by a broad, ten­di­nous ex­pan­sion, which covers the knee-joint, and is attached to the femur and the tibio-fibula by anterior and posterior bands respectively; it ends internally in a con­cave apo­neur­ot­ic arch: the second head is a thin, tendinous slip, arising from the common tendon of the triceps as this lies on the knee-joint. The muscle is thickest near its origin, and then gradually diminishes in size as it passes backwards; the superficial surface is convex, the deep surface is flat. By tracing the tendons of origin, they are seen soon to unite and form a common flat ten­di­nous sur­face, broad in front, con­trac­ted behind; this apo­neur­osis lies in a plane running ob­lique­ly from the deep sur­face towards the super­ficial sur­face, without, how­ever, reaching this. The muscular fibres arise from both sur­faces of the apo­neur­osis, the fibres of the two sides d­iverg­ing slightly as they pass back­wards so as to be inclined at a small angle to each other. The fibres are inserted into a fibrous ex­pan­sion (Ap) which lies on the super­ficial sur­face of the muscle; thin and slight in front, this apo­neur­osis rapidly thickens pos­ter­ior­ly until it passes into the tendo Achillis.

128. M. tibialis posticus (Fig. 86 t.p.).

Covered by the gastrocnemius this muscle occupies the whole of the inner and upper surfaces of the tibio-fibula, from which it arises by numerous fibres. Opposite the hinder extremity of the bone the muscle becomes free and passes somewhat abruptly into a tendon, which courses behind and over the malleolus internus, on to the dorsum of the foot, and is here inserted into the anterior extremity of the astragalus. I cannot agree with Dugès that this muscle corresponds with the soleus (Ecker).

129. M. extensor cruris brevis (Fig. 87 ec).

Covered by the strong fascia cruris, and lying between the m. tibialis anticus and the tibio-fibula, this muscle arises by a long tendon from the inner condyle of the femur; it passes backwards in the groove on the anterior extremity of the tibio-fibula, covered by the tendon of the triceps femoris, and is then inserted by muscular fibres into the outer surface of the tibio-fibula almost as far as the posterior third of the bone. (Dugès regards this muscle as the upper, i. e. anterior, portion of the tibialis anticus.)

130. M. tibialis anticus (Figs. 80, 81, 87 ta).

The tendon of origin of this muscle is attached to the femur near the tendon of the m. extensor cruris brevis, and to the joint-ligaments. The muscle is placed under the fascia cruris, its long tendon of origin passing beneath the tendon of the triceps in a special sheath through the joint; the tendon then gains a muscular belly which bifurcates at about the middle of the leg, forming two muscular masses, coursing along the outer and the inner side of the leg respectively. The latter is inserted into the dorsal surface of the astragalus by a tendon, and the former into the dorsal surface of the calcaneus in a similar manner. The muscle extends the foot and flexes the tarsus; the latter movement is very distinct on account of the insertion of the muscle being so near the hypomochlion.

131. M. flexor tarsi anterior (Ecker), (Fig. 87 Ft).

This muscle arises where the insertion of the extensor cruris brevis ceases, from the middle of the under surface of the tibio-fibula, and passes backwards between the two tendons of the m. tibialis anticus along the outer side of this muscle, to be inserted by a tendon into the inner side of the anterior articular extremity of the astragalus and the fascia dorsalis pedis.

132. M. peroneus (Figs. 80 pe, 87 p).

This is a strong muscle which is attached by a long tendon of origin to the hinder extremity of the femur and the ligaments of the knee-joint. The tendon runs in a sheath through the joint and posteriorly becomes muscular; the muscle passes downwards on the outer side of the tibio-fibula to be inserted into the malleolus externus of this bone and into the anterior extremity of the calcaneus. It has an action similar to that of the m. tibialis anticus.

III. Muscles of the Foot.

A. Muscles on the Plantar Surface.

133. Aponeurosis plantaris (Fig. 88 A.p.).

As already mentioned, the tendon of the m. gastrocnemius is, at the heel, continued into a strong aponeurosis, and possesses at this place a thickening‍48. The aponeurosis is of triangular form, the base directed towards the toes and attached to these. The lateral borders of this triangle are continued into weaker fasciae, which are attached to the two long tarsal bones. The inner border in particular gives a strong bundle of fibres to the astragalus, and is thus connected with the fascia of the dorsum of the foot; externally this aponeurosis is attached to a cartilage (Dugès, os sesamoïde, l. c., n. 66), situated on the plantar surface of the joint between the calcaneus and the os metatarsi IV.

134. Ligamentum calcanei (Ecker), (Figs. 88, 89 l.c.).

If the tendo Achillis be divided and the aponeurosis plantaris reflected towards the toes, there is seen, arising from the posterior head of the tibio-fibula, in its whole breadth, a ligament (between the tib. posticus and peroneus). This ligament forms a firm surface on which the thickened portion of the tendo Achillis may move, and which evidently represents the tuberosity of the heel bone. I have therefore named the entire structure the ligamentum calcanei.

Several muscles arise from this ligament, viz.:‍—

135. M. extensor tarsi (Klein), (Figs. 88, 89 e.t.).

Covered by the two succeeding muscles, this muscle arises from the ligamentum calcanei, runs backwards, and is inserted into the whole length of the plantar surface of the astragalus. It extends the foot.

136. M. plantaris (Figs. 88, 89 p).

This takes its origin from the ligamentum calcanei to the inner side and below the last muscle. It passes backwards and is inserted into the dorsal surface of the aponeurosis plantaris.

137. M. flexor digitorum III, IV, V longus (Ecker), (Figs. 88, 89 F.l.).

This muscle also arises from the ligamentum calcanei to the outer side of the m. plantaris. It runs backwards over the aponeurosis plantaris, and at the free margin of this passes somewhat suddenly into a strong tendon, which traverses an aponeurotic canal, formed by fibres of the aponeurosis passing above and below the tendon, from the cartilaginous enlargement in the tendon to the median border of the aponeurosis. The tendon forms three slips for the fifth, fourth, and third toes: these are slightly attached to the aponeurosis, but reach beyond its free border to be inserted into the terminal phalanges of the toes mentioned, and are held down by fibrous bands. (The small m. lumbricales arising from these tendons are described below.)

138. M. flexor digitorum I, II longus (Ecker), (Figs. 88, 89 F.l′.).

The tendons, by means of which the terminal phalanges of the first and second toes are flexed, arise directly from the posterior border of the aponeurosis.

139, 140. MM. transversi plantae (Ecker), (Fig. 89 t.p., t.p′.).

The movements of the aponeurosis and through it the movements of the tendons attached to it are influenced not only by the m. gastrocnemius and plantaris, but also by two other muscles, which together have been described as the flexor dig. longus internus (Klein), or as the tarso-sous-phalangettien (Dugès, 221).

a. M. transversus plantae posterior (t.p.).

This takes its origin from the plantar cartilage, widens as it courses backwards and inwards to be inserted into the dorsal surface of the aponeurosis plantaris; from this the tendons for the first and second toes (flexor dig. longus I and II) arise, thus there is no direct connection between the muscular fibres of the two muscles.

b. M. transversus plantae anterior (t.p′.).

This muscle is covered by the last; broader anteriorly, it arises from the calcaneum, and is inserted to the inner side of the last muscle into the dorsal surface of the aponeurosis. This muscle, like that just described, is not continued directly into the tendon of the flexor of the toes, they cannot therefore be regarded as flexors of the toes.

141 to 149. Musculi lumbricales (Fig. 89 l.1–5).

(A.) From the posterior border of the aponeurosis plantaris arise:‍—

(1) M. lumbricalis digiti I (l.1).

This is inserted into the anterior extremity of the proximal phalanx.

(2) M. lumbricalis digiti II (l.2).

Similarly inserted.

(3 and 4) MM. lumbricales digiti III (l.3).

One of these (l3) is inserted into the anterior extremity of the basal phalanx, the other (l3′) into a corresponding position on the middle phalanx.

(5) M. lumbricalis digiti IV.

Inserted into the anterior extremity of the basal phalanx.

(B.) Arising from the tendons of the flexor longus III, IV, V:

(6 and 7) MM. lumbricales digiti IV (l.4′. and l.4″.).

The first (l.4′) is inserted into the posterior end of the basal phalanx, the second (l.4″) in a similar position into the second phalanx.

(8) M. lumbricalis digiti V (l.5.).

This arises from the tendon for the fifth toe, runs backwards as a thin tendon alongside that of the flexor, and is inserted into the middle phalanx.

Special Muscles of the Separate Toes.

(I.) Muscles of the rudimentary great toe.

150. M. abductor hallucis (Figs. 88 a.h., 90).

This muscle arises from the inner border of the aponeurosis plantaris, at the spot where the m. plantaris is inserted, it may therefore almost be regarded as a continuation of this muscle; it is inserted into the anterior border of the rudimentary toe.

(II.) Muscles of the great and first toes.

151. M. adductor longus digiti I (Figs. 89, 90 ad.l1).

This powerful muscle arises from the plantar surface of the calcaneum and astragalus; its fibres converge towards a tendon lying in its middle, which becomes free towards its posterior end; the tendon passing inwards under the ligamentum tarsi transversum through a groove on the hinder extremity of the astragalus in an arched direction, to be inserted into the os naviculare, which bears the rudimentary great toe and the os metatarsi I.

(III.) Muscles of the first toe.

152. M. abductor longus digiti I (Figs. 88 al.1, 90 a.b.1).

It takes its origin from the inner border of the aponeurosis plantaris, and lies on the plantar surface of the abductor hallucis. Its tendon runs in the hollow which the great toe forms, and is inserted into the inner side of the os metatarsi I.

153. M. flexor brevis digiti I (Fig. 90 F.b.1).

A small, thin muscle, which arises from the anterior extremity of the os metatarsi II, and is inserted into the basal phalanx of the first toe. In this small muscle, and also in the m. lumbrical. dig. V (Fig. 89 l.5.), the nerve distribution may be very well seen.

154. M. opponens dig. I (Fig. 90 op).

This is situated to the inner side of the preceding muscle, arises from the os metatarsi II somewhat narrow, widens in a fan-like manner towards the os metatarsi I, into the anterior half of which it is inserted.

(IV.) Muscles of the second toe.

155. M. flexor metatarsi dig. II (Fig. 90 F.m.2).

Like the corresponding muscle of the second toe (n. 155), this arises by a small tendon from the hinder extremity of the calcaneum, runs backwards and is inserted into the plantar surface of the os metatarsi III. The greatest portion of the muscle lies beneath the m. transversus metatarsi (tm), the most anterior portion, however, lies above this. Dugès has described this latter portion as a special muscle (n. 176, metatarso-métatarsien du III), the same description holds good for the second toe (n. 177, Dugès).

158. M. flexor dig. III proprius (Ecker), (Fig. 91 Fp3).

Like the corresponding muscle of the second toe, this arises from the plantar surface of the os metatarsi III, and is inserted by a thin tendon into the plantar surface of the anterior extremity of the first phalanx.

159. M. flexor phalangum proprius digiti III (Ecker), (Fig. 91 F.ph.3).

This arises by tendon from the plantar surface of the basal phalanx, and is inserted into the anterior extremity of the terminal phalanx.

(VI.) Muscles of the fourth toe.

160. M. flexor metatarsi dig. IV (Fig. 91 F.m.4).

Similarly to the corresponding muscle of the third toe, this one arises from the hinder extremity of the calcaneum, and is inserted into the anterior portion of the plantar surface of the os metatarsi IV, but not into the greater portion of this surface, as in the second and third os metatarsi.

161. M. flexor dig. IV proprius (Fig. 91 Fp4).

The origin and insertion are similar to those of the muscles of the second and third toes.

162. M. flexor brevis dig. IV.

A small muscle, which arises with the m. flexor brevis of the fifth toe, from enlargement of aponeurosis plantaris, and is inserted into the basal phalanx of the fourth toe.

163. M. flexor phalangum proprius dig. IV anterior (Fig. 91 F.ph.4).