of the great toe, the short border with the scaphoid bone. The small extremity (edge) is sharp [and looks upwards]; the larger extremity (base) rounded into a broad tuberosity.

Articulations.. With four bones: scaphoid, middle cuneiform, and first two metatarsal bones.

Attachment of Muscles. To the tibialis anticus and posticus.

The MIDDLE CUNEIFORM is the smallest of the three; it is wedge-shaped, the broad extremity being placed upwards, the sharp end downwards in the foot. It presents for examination four articular surfaces and two extremities. The anterior and posterior surface have nothing worthy of remark. One of the lateral surfaces has a long articular facet, extending its whole length, for the internal cuneiform; the other has only a partial articular facet for the external cuneiform bone.

If the bone be held so that the square extremity look upwards, the broadest edge of the square being towards the holder, the small and partial articular surface will point to the side to which the bone belongs.

-

Articulations. With four bones: scaphoid, internal and external cuneiform, and second metatarsal bone.

The EXTERNAL CUNEIFORM is intermediate in size between the two preceding, and placed, like the middle, with the broad end upwards, and sharp extremity downwards. It presents for examination five surfaces, and a superior and inferior extremity. The upper extremity is flat, of an oblong square form, and bevelled posteriorly, at the expense of the outer surface, into a sharp edge.

If the bone be held so that the square extremity look upwards, and the sharp border backwards, the bevelled surface will point to the side to which the bone belongs.

Articulations. With six bones: scaphoid, middle cuneiform, cuboid, and second, third, and fourth metatarsal bone.

Attachment of Muscles. To the flexor brevis pollicis.

The CUBOID BONE is irregularly cuboid in shape, and marked on its under surface by a deep groove, for the tendon of the peroneus longus muscle. It presents for examination, six surfaces, three articular, and three non-articular. The non-articular surfaces are, superior, which is slightly convex, and assists in forming the dorsum of the foot; inferior, marked by a prominent ridge, the tuberosity, and a deep groove for the tendon of the peroneus longus; and external, the smallest of the whole, and deeply notched by the commencement of the peroneal groove. The articular surfaces are, posterior, of large size, and concavo-convex, to articulate with the os calcis; anterior, of smaller size, divided by a slight ridge into two facets, for the fourth and fifth metatarsal bones; and internal, a small oval articular facet, upon a large and quadrangular surface, for the external cuneiform bone.

If the bone be held so that the plantar surface, with the peroneal groove, look downwards, and the largest articular surface backwards, the small non-articular surface, marked by the deep notch, will point to the side to which the bone belongs.

Articulations. With four bones: os calcis, external cuneiform, fourth and fifth metatarsal bone, and sometimes the scaphoid.

Attachment of Muscles. To two: flexor brevis pollicis, and adductor pol

licis.

Upon a consideration of the articulations of the tarsus it will be observed, that each bone articulates with four adjoining bones, with the exception of the calcaueum, which articulates with two, and the external cuneiform with six.

Development. By a single centre for each bone, with the exception of the os

calcis, which has an epiphysis for its posterior tuberosity. The centres appear in the following order; calcanean, sixth month; astragalan, seventh month; cuboid, tenth month; external cuneiform, end of the first year; internal cuneiform, during the third year; middle cuneiform and scaphoid during the fourth year. The epiphysis of the calcaneum appears at the ninth year, and is united with the diaphysis at about the fifteenth.

FIG. 101.

[When we consider the tarsus as a whole, we find that its antero-posterior diameter is about twice as great as its transverse, and that its seven bones are disposed in two rows; the first or tibial row, is formed by the os calcis and the astragalus, which are placed not side by side, but one (the astragalus) above and resting upon the other. The second or metatarsal row, is composed of the scaphoid, on the inner side, and the three cuneiform bones, which are articulated to its anterior surface; and on the outer side, of the cuboid. These bones collectively form the posterior half of the foot, and constitute an arch, on the summit of which the weight of the leg is received; the plantar aspect of the arch is deeply excavated both antero-posteriorly and transversely, which not only secures to the structure the peculiar advantages of such a mechanism, but protects from pressure, during standing or walking, the vessels and nerves which are here located. The posterior extremity of the tarsus is narrow and non-articular, being formed by the posterior tuberosity of the calcaneum, but it progressively increases in width, forwards, the anterior extremity being formed by the three cuneiform bones and the cuboid, which present a sinuous articular border for the bases of the metatarsal bones. This border has a direction obliquely forwards from the outer to the inner side of the foot-hence the inner edge or border of the tarsus is longer, and extends further forwards than the outer. This point, taken in connection with shortness of the middle cuneiform, admitting of a dove-tailing of the base of the second metatarsal bone into this border is of great importance in reference to Hey's operation of amputation at the tarso-metatarsal articulation.]

The METATARSAL BONES, five in number, are long bones, and divisible therefore into a shaft and two extremities. The shaft is prismoid, and compressed from side to side; the posterior extremity, or base, is square-shaped, to articulate with the tarsal bones, and with each other; the anterior extremity presents a rounded head, circumscribed by a neck, to articulate with the first row of the phalanges.

14

SOLE OF THE LEFT FOOT. tuberosity of the os calcis. tuberosity. *Posterior

1. Inner

2. Outer tuberosity.

3. Groove for the tendon of the flexor longus digitorum; this figure indicates also the sustentaculum tali, upon which it is placed. 4. Rounded head of the astragalus. 5. Scaphoid bone. 6. Its tuberosity. 7. Internal cuneiform bone; its broad extremity. 8. Middle cuneiform bone. 9. External cuneiform bone. 10, 11. Cuboid bone. 11. Groove for the tendon of the peroneus longus; the prominence between this groove and figure 10 is the tuberosity of this bone. 12, 12. Metatarsal bones. 13, 13. First phalanges. 14, 14. Second phalanges of the four lesser toes. 15, 15. Third, or ungual phalanges of the four lesser toes. 16. Last phalanx of the great

toe.

Peculiar Metatarsal Bones. -The first is shorter and larger than the rest, and forms part of the inner border of the foot; its posterior extremity presents only one lateral articular surface, and an oval

rough prominence beneath, for the insertion of the tendon of the peroneus longus. The anterior extremity has, on its plantar surface, two grooved facets, for sesamoid bones.

The second is the longest and largest of the remaining metatarsal bones; it presents at its base three articular facets, for the three cuneiform bones; a large oval facet, but often no articular surface, on its inner side, to articulate with the metatarsal bone of the great toe, and two externally, for the third metatarsal bone.

The third may be known by two facets on the inner side of its base, corresponding with the second, and may be distinguished by its smaller size.

The fourth may be distinguished by its smaller size, and by having a single articular surface on each side of the base.

The fifth is recoguised by its broad base, and by the large tuberosity at its

outer side.

Development. Each bone by two centres; one for the body and one for the digital extremity in the four outer metatarsal bones; and one for the body, the other for the base, in the metatarsal bone of the great toe. Ossification appears in these bones at the same time with the vertebræ; the epiphyses commencing with the great toe and proceeding to the fifth, appear towards the close of the second year, consolidation being effected at eighteen.

Articulations. With the tarsal bones by one extremity, and first row of phalanges by the other. The number of tarsal bones with which each metatarsal articulates from within outwards, is the same as between the bones of the metacarpus and carpus, one for the first, three for the second, one for the third, two for the fourth, and one for the fifth, forming the cipher 13121.

Attachment of Muscles. -To fourteen: to the first, peroneus longus and first dorsal interosseous; to the second, two dorsal interossei and transversus pedis ; to the third, two dorsal and one plantar interosseous, adductor pollicis and transversus pedis; to the fourth, two dorsal and one plantar interosseous, adductor pollicis and transversus pedis; to the fifth, one dorsal and one plantar interosseous, peroneus brevis, peroneus tertius, adductor minimi digiti, flexor brevis minimi digiti, and transversus pedis.

PHALANGES. There are two phalanges in the great toe and three in the other toes, as in the hand. They are long bones, divisible into a central portion and extremities.

The phalanges of the first row are convex above, concave on the under surface, and compressed from side to side. The posterior extremity has a single concave articular surface, for the head of the metatarsal bone; the anterior extremity, a pulley-like surface, for the second phalanx.

The second phalanges are short and diminutive, but somewhat broader than those of the first row.

The third or ungual phalanges, including the second phalanx of the great toe, are flattened from above downwards, spread out laterally at the base to articulate with the second row, and at the opposite extremity to support the nail and the rounded extremity of the toe.

Development. By two centres; one for the body and one for the metatarsal extremity. Ossification commences in these bones after that in the metatarsus, appearing firstly in the last phalanges, then in the first, and lastly in the middle The bones are completed at eighteen.

row.

Articulations. The first row with the metatarsal bones and second phalanges; the second, of the great toe, with the first phalanx; of the other toes, with the first and third phalanges; the third, with the second row.

Attachment of Muscles. To twenty-three: to the first phalanges; great toe, innermost tendon of the extensor brevis digitorum, abductor pollicis, adductor pollicis, flexor brevis pollicis, and transversus vedis; second toe, first dorsal and first

plantar interosseous and lumbricalis; third toe, second dorsal and second plantar interosseous and lumbricalis; fourth toe, third dorsal and third plantar interosseous and lumbricalis; fifth toe, fourth dorsal interosseous, abductor minimi digiti, flexor brevis minimi digiti and lumbricalis. Second phalanges: great toe, extensor longus pollicis, and flexor longus pollicis; other toes, one slip of the common tendon of the extensor longus and extensor brevis digitorum, and flexor brevis digitorum. Third phalanges; two slips of the common tendon of the extensor longus and extensor brevis digitorum, and the flexor longus digitorum.

SESAMOID BONES [osteids]. These are small osseous masses, developed in those tendons which exert a certain degree of force upon the surface over which they glide, or where, by continued pressure and friction, the tendon would become a source of irritation to neighbouring parts, as to joints. The best example of a sesamoid bone is the patella, developed in the common tendon of the quadriceps extensor, and resting against the front of the knee-joint. Besides the patella, there are four pairs of sesamoid bones included in the number of pieces which compose the skeleton, two on the metacarpo-phalangeal articulation of each thumb, and existing in the tendons of insertion of the flexor brevis pollicis, and two upon the corresponding joint in the foot, in the tendons of the muscles inserted into the base of first phalanx. In addition to these there is often a sesamoid bone on the metacarpo-phalangeal joint of the little finger; and on the corresponding joint in the foot, in the tendons inserted into the base of the first phalanx; there is one also in the tendon of the peroneus longus muscle, where it glides through the groove in the cuboid bone; sometimes in the tendons, as they wind around the inner and outer malleolus; in the psoas and iliacus, where they glide over the body of the os pubis: and in the external head of the gastrocnemius.

The bones of the tympanum, as they belong to the apparatus of hearing, will be described with the anatomy of the ear.

CHAPTER III.

OF THE LIGAMENTS.

THE bones are variously connected with each other in the construction of the skeleton, and the connexion between any two bones constitutes a joint or articulation. If the joint be immovable, the surfaces of the bones are applied in direct contact; but if motion be intended, the opposing surfaces are expanded and coated by an elastic substance named cartilage; a fluid secreted by a membrane closed on all sides lubricates their surface, and they are firmly held together by means of short bands of glistening fibres, which are called ligaments (ligare, to bind). The study of the ligaments is termed syndesmology (ovv, together, desμos, bond), which, with the anatomy of the articulations, forms the subject of the present chapter.

The forms of articulation met with in the human frame may be considered under three classes: Synarthrosis, Amphi-arthrosis, and Diarthrosis.

SYNARTHROSIS (ovv, äpopwors, articulation) is expressive of the fixed form of joint in which the bones are immovably connected with each other. The kinds of synarthrosis are four in number. Sutura, Harmonia, Schindylesis, Gomphosis. The characters of the three first have been sufficiently explained in the preceding chapter, p. 82. It is here only necessary to state that, in the construction of sutures, the substance of the bones is not in immediate contact, but separated by

a layer of membrane, which is continuous externally with the perieranium and internally with the dura mater. It is the latter connexion which gives rise to the resistance experienced in tearing the calvaria from the dura mater. Cruveilhier describes this interposed membrane as the sutural cartilage; I never saw any structure in the sutures which could be regarded as cartilage, and the history of the formation of the cranial bones would suggest a different explanation. The fourth, Gomphosis (youpos, a nail), is expressive of the insertion of one bone into another, as a nail is fixed into a board; this is illustrated in the articulation of the teeth with the alveoli of the maxillary bones.

AMPHI-ARTHROSIS (dupi, both, apOpuses) is a joint intermediate in aptitude for motion between the immovable synarthrosis and the movable diarthrosis. It is constituted by the approximation of surfaces partly coated with cartilage lined by synovial membrane, and partly connected by interosseous ligaments, or by the intervention of an elastic fibro-cartilage which adheres to the ends of both bones. Examples of this mode of articulation are seen in the union between the bodies of the vertebræ, the sacrum with the coccyx, the pieces of the sternum, the sacroiline and pubic symphyses (our piew, to grow together), and according to some, the necks of the ribs, with the transverse processes.

DIARTHROSIS (dia, through, apposts) is the movable articulation, which constitutes by far the greater number of the joints of the body. The degree of motion in this class has given rise to a subdivision into three genera, Arthrodia, Ginglymus, and Enarthrosis.

Arthrodia [apopov, a joint, apw, to adapt] is the movable joint in which the extent of motion is slight and limited, as in the articulations of the clavicle, ribs, articular processes of the vertebræ, axis with the atlas, radius with the ulna, fibula with the tibia, carpal and metacarpal, tarsal and metatarsal bones.

Ginglymus (yyyavuòs, a hinge), or hinge-joint, is the movement of bones upon ench other in two directions only, viz., forwards and backwards; but the degree of motion may be very considerable. Instances of this form of joint are numerous; they comprehend the elbow, wrist, metacarpo-phalangeal, and phalangeal joints in the upper extremity; the knee, ankle, metatarso-phalangeal, and phalangeal joints in the lower extremity. The lower jaw may also be admitted into this category, as partaking more of the character of the hinge-joint than of the less movable arthrodia.

The form of the ginglymoid joint is somewhat quadrilateral, each of its four sides being provided with a ligament, which is named from its position, anterior, posterior, internal lateral, or external lateral. The lateral ligaments are thick and strong, and the chief bond of union between the bones. The anterior and posterior are thin and loose, in order to permit the required extent of

movement.

Enarthrosis (1», in, apposts) is the most extensive in its range of motion of all the movable joints. From the manner of connexion and form of the bones in this articulation, it is called the ball-and-socket joint. There are two instances in the body, namely, the hip and the shoulder.

I have been in the habit of adding to the preceding the carpo-metacarpal articulation of the thumb, although not strictly a ball-and-socket joint, from the great extent of motion which it enjoys, and from the nature of the ligament connecting the bones. As far as the articular surfaces are concerned, it is rather a double than a single ball-and-socket; and the whole of these considerations remove it from the simple arthrodial and ginglymoid groups.

The ball-and-socket joint has a circular form; and, in place of the four distinct ligaments of the gingly mus, is inclosed in a bag of ligamentous membrane, called, oapswar doam CNÉ,

The kinds of articulation may be shown in a tabular form, as follows: