The cuboid, by an oval facet on its inner surface articulates with the external cuneiforn bone. Interosseous, dorsal, and plantar ligaments bind them together. By dividing the dorsal ligament and insinuating the knife between the two bones the interosseous ligament may be detected. It is the strongest of the three ligaments.

The synovial membrane which lines the scapho-cuneiform articulation is prolonged into the cubo-cuneiform joint. and also into the scapho-cuboid joint when this exists.

Tarso-metatarsal Articulations.-The bases of the five metatarsal bones articulate with the three cuneiform bones and the cuboid bone, and are very firmly attached to them by dorsal, plantar, and interosseous ligaments.

The dorsal ligaments are flat distinct bands which can readily be defined. One such ligament passes to the base of the first metatarsal from the internal cuneiform; three, one from each of the cuneiform bones, proceed to the base of the second metatarsal; one extends from the external cuneiform to the base of the third metatarsal; two, of which one proceeds from the external cuneiform, and the other from the cuboid, go to the base of the fourth metatarsal; and one passes from the cuboid to the base of the fifth metatarsal.

The plantar ligaments are not so regularly disposed. Those in connection with the first and second metatarsal bones are very strong. Some of the bands have an oblique direction, and those which go to the bases of the three middle metatarsal bones are more or less connected with the sheath of the tendon of the peroneus longus, and therefore with the long plantar ligament.

To bring the interosseous ligaments into view, divide freely the dorsal ligaments, and then forcibly bend the metatarsus downwards upon the tarsus. The interosseous ligaments will resist this proceeding, and on looking into. the joints they will be seen stretched and tense. If the force be continued they will rupture. The interosseous ligaments are three in number, viz. an internal, a middle, and an external.

The internal interosseous ligament is an exceedingly strong band, which passes forwards and outwards from the anterior part of the outer surface of the internal cuneiform bone to the adjacent surface of the base of the second metatarsal bone. The middle interosseous ligament is small, and passes forwards between the anterior part of the inner surface of the external cuneiform and the adjacent surface of the base of the second metatarsal. The external interosseous ligament passes from the outer surface of the external cuneiform bone to the outer side of the base of the third metatarsal. One interosseous ligament therefore passes from the internal cuneiform bone and two from the external cuneiform, and of these two are attached to the base of the second, and the third to the base of the third metatarsal bone.

Tarso-metatarsal Articular Surfaces.-The manner in which the metatarsus is implanted upon the tarsus should now be examined. The first metatarsal rests upon the internal cuneiform, and this joint possesses a separate synovial membrane. The second metatarsal rests upon the middle cuneiform, but its base is grasped by the projecting anterior ends of the internal and external cuneiform bones, with both of which it articulates, and with both of which it is connected by interosseous ligaments. wonder then that this metatarsal should possess so little power of independent movement, and present a difficulty to the surgeon when he is called upon to amputate the fore-part of the foot through the tarso-metatarsal articulation (Hey's operation). The third metatarsal rests upon the external cuneiform. The synovial membrane which lines the joints between the tarsus and the second and third metatarsal bones is continuous with that which is present between the internal and middle cuneiform bones, and through this with the scapho-cuneiform synovial membrane. The bases of the fourth and fifth metatarsal bones are supported by the cuboid, but that of the fourth, by its inner margin, articulates also with the external cuneiform. A separate synovial membrane is present in

the articulation between the two outer metatarsal bones and the tarsus.

Intermetatarsal Joints.-The bases of the metatarsal bones, with the exception of the first, articulate with each. other, and are very firmly bound together.

The ligaments which connect the bases of the four outer metatarsal bones are dorsal, plantar, and interosseous. To bring the interosseous ligaments into view it is necessary to divide the dorsal ligaments, and then forcibly separate the bases of the bones from each other. They are strong bands which pass between the non-articular portions of the basal parts of the bones. They constitute the chief bond of union.

In addition to these basal ligaments, the strong transverse metatarsal ligament unites the distal extremities of the metatarsal bones. This ligament has been previously

described (p. 303).

Synovial Cavities of the Foot.-There are six separate synovial cavities in connection with the tarsal, tarso-metatarsal, and intermetatarsal articulations, viz.-(1) in the joint between the posterior facets of the astragalus and os calcis; (2) in the calcaneo-cuboid joint; (3) in the joint. formed by the head of the astragalus, the scaphoid, the sustentaculum tali, and the two calcaneo-scaphoid ligaments; (4) a complicated synovial membrane which lines the scapho-cuneiform articulations, and is prolonged forwards between the cuneiforms, and also between the cuboid and external cuneiform bones. This synovial membrane, however, is not confined to the tarsus, but reaches forwards into the articulation between the second and third metatarsal bones and the tarsus, as well as into the joints between the bases of the second, third, and fourth metatarsal bones; (5) a separate synovial lining for the joint between the first metatarsal and the internal

1 The external interosseous tarso-metatarsal ligament, which passes from the external cuneiform bone (frequently from the cuboid bone) to the base of the third metatarsal bone, separates the articulations of the fourth and fifth metatarsal bones from the general tarsal articular cavity.

cuneiform; (6) a distinct synovial membrane for the articulations between the cuboid and the two outer metatarsal bones. This is prolonged forwards into the joint. between the bases of these two metatarsals.

Metatarso-phalangeal and Interphalangeal Joints.These joints are constructed upon a plan almost identical with that of the corresponding joints of the upper extremity. For the detailed description the student is therefore referred to p. 161. In the metatarso-phalangeal joint of the great toe the thick inferior ligament or fibrous plate holds two large sesamoid bones, which slide upon grooved surfaces on the head of the metatarsal bone.

Movements. The movements which take place in the tarso-metatarsal, intermetatarsal, and in the majority of the tarsal joints, are of a gliding character. In the joints between the astragalus and scaphoid, and also between the os calcis and the cuboid, movements of a wider range are possible. It is here that the movements of inversion and eversion of the foot chiefly take place.

The first and the fifth metatarsal bones enjoy a considerable degree of mobility. The second metatarsal is so tightly grasped by the internal and external cuneiform bones, and so firmly bound to the tarsus by its basal ligaments, that only a slight degree of movement is possible.

At the metatarso-phalangeal joints, flexion, extension, abduction, and adduction, are allowed; whilst the interphalangeal joints only permit of flexion and extension.

In the erect posture the parts of the foot which are chiefly concerned in transmitting the weight of the body to the ground are the heel, the head of the first metatarsal bone, and the shaft of the fifth metatarsal bone. Rather more than the middle third of the inner border of the foot is raised above the ground. The outer border of the foot is more or less in contact with the ground in its entire extent, whilst the tips of the toes rest lightly on the ground. In walking(1) the heel is brought down; (2) the sole and toes follow; (3) the heel is raised, and the weight of the body is transferred to the heads of the metatarsal bones and the toes. In the second and third parts of this operation the arches of the foot are flattened to a certain extent, but more especially in the third part of the process is the transverse arch spread out. Great elasticity is thus given to the step.

The muscles which are chiefly concerned in producing eversion of the foot are the three peroneal muscles; those which operate as invertors of the foot are the tibialis anticus and the tibialis posticus.

The extensors of the toes are the extensor longus hallucis, the extensor brevis digitorum, and the extensor longus digitorum. The lumbrical muscles, and the interosseous muscles, through their insertions into the extensor tendons of the four outer toes, operate as extensors of the second and third phalanges.

The flexors of the proximal phalanges are the lumbricales, interossei, flexor brevis hallucis, and flexor brevis minimi digiti. The flexor of the second phalanges is the flexor brevis digitorum; whilst the flexors of the distal phalanges are the flexor longus digitorum, the musculus accessorius, and the flexor longus hallucis.

Abduction and adduction of the toes at the metatarso - phalangeal joints are produced by the interosseous muscles, the abductor hallucis, the adductor obliquus hallucis, the adductor transversus hallucis, and the abductor minimi digiti. The movements of abduction and adduction take place with reference to a line drawn through the second toe.

ABDOMEN.

WHEN the body is brought into the dissecting-room, it is first placed in the lithotomy position (Fig. 71). A stout cord or bandage is doubled and passed in the form of a running noose over each hand of the subject, so as to grasp the wrist when tightened. The hands are then drawn downwards and the feet upwards until the palm of each hand rests upon the outer aspect and dorsum of the corresponding foot. In this position they must be securely fixed by passing the cord once or twice round the instep, and then tying a knot upon the inner aspect of the foot. The subject must now be drawn towards the end of the table until the breech projects slightly over the edge. A block is introduced under the pelvis, and the cords carried downwards and fastened on each side to the leg of the table, so as to keep the lower limbs well apart from each other. A third cord must next be passed behind the flexed knee-joints, and then round the neck of the subject,