FIG. 65.-Bones of the left hand, palmar surface (Gray).

(eighth fetal week) and one for the head (third year; they coössify by the twentieth year). The third metacarpal articulates with the os magnum; on the ulnar side it has two small

facets for the fourth metacarpal, and a single facet on the radial side for the second metacarpal; the outer angle of its base is the styloid process. The fourth metacarpal has two facets for the unciform and the os magnum, a single facet on the ulnar side for the fifth metacarpal, and two small ones on the radial side for the third metacarpal. The fifth metacarpal articulates with the unciform by a concavo-convex facet, has only a lateral facet on the radial side for the fourth metacarpal, and on the ulnar side a prominent tubercle for the extensor carpi ulnaris tendon.

Describe the phalanges.

They are fourteen in number-three for each finger, and two for the thumb-they are long bones, having a shaft, base, and condyles, except those of the distal row. The bases of the first row, cup-shaped, articulate with the heads of the metacarpals; those of the second and third have a double concavity, separated by a median ridge, and articulate with the condyles of the row above; the distal extremities of the ungual phalanges have rough, horse-shoe shaped tubercles, ungual processes, on their palmar surfaces for attachment of the pulp of the finger; they ossify by one center for the shaft (eighth fetal week), and one for the base (third to fifth year); uniting in from eighteen to twenty years.

BONES OF THE LOWER EXTREMITY. They include those of the hip, thigh, leg, and foot.

Describe the femur.

The Thigh.

It is the longest bone of the skeleton, and inclines toward its fellow to bring the knee-joint near the center of gravity during walking, this obliquity being greater in the female, from the breadth of the pelvis, and in a short person than in a tall one of either sex.

The head (Fig. 66), forming rather more than a hemisphere, directed upward, inward, and forward, has behind and below its center the fossa capitis for the ligamentum teres. The neck, joining the head with the shaft, is flattened and pyramidal; in the adult male it forms an obtuse angle with the shaft of about

125°. After ossification is completed, twenty years, this angle does not change nor does the neck become horizontal.

The great trochanter is a large, irregular, quadrilateral eminence, directed upward, outward, and backward, marked on its external surface by a diagonal line for the gluteus medius; below and behind this is a smooth surface for a bursa beneath the gluteus maximus; in front is inserted the gluteus minimus; superiorly is the pyriformis; and upon its inner surface is the digital fossa for the tendon of the obturator externus muscle; and above that the internal obturator and gemelli muscles are inserted.

The lesser trochanter (Fig. 67), small and conical, projects from the lower back part of the base of the neck, receiving the insertion of the psoas muscle above and the iliacus below.

The anterior and posterior intertrochanteric lines connect these processes, the latter being the more prominent, while to the former is attached the anterior portion of the capsular ligament. At the middle of the posterior intertrochanteric line is a tubercle for the quadratus femoris muscle, sometimes a linea quadrati.

The shaft, broad and cylindroid at either extremity, narrow and triangular in the center, slightly curved forward, has its medullary foramen at the junction of the middle and lower thirds of its posterior surface, directed upward; and from its anterior surface arise the crureus and subcrureus muscles.

The linea aspera, a prominent longitudinal ridge occupying the middle third of the posterior surface, has an external and an internal lip, and an intermediate space; above, it divides into three lines, one directed upward to the base of the greater, one to the base of the lesser trochanter, a third, the most internal, continuous with the anterior intertrochanteric line, forming with it the spiral line, while below the linea aspera bifurcates to inclose the smooth popliteal space, the inner division grooved for the femoral vessels. In general terms, this line and its subdivisions have attached the following muscles: the vastus internus and externus, the pectineus, the three adductors, the short head of the biceps, and the gluteus maximus.

Of the two condyles, the internal is the longer by about half an inch, to bring both condyles on the same horizontal plane in the normally oblique position of the femur; above each condyle, behind, is a depression for the gastrocnemius (above the

external the plantaris muscle also originates); separating them is the intercondyloid notch, to whose sides are attached the crucial ligaments; in front, the condyles form a continuous articular surface, the trochlea; the outer, as well as the inner, condyle presents an epicondyle upon its free surface for the lateral ligaments, beneath which, on the outer condyle, is a groove for the tendon of origin of the popliteus muscle; above the internal condyle is a small adductor tubercle for the tendon of the adductor magnus.

Give the development of the femur.

By five centers: one for the shaft (fifth fetal week); one for the condyles (ninth fetal month); one for the head (end of the first year); one for the greater trochanter (fourth year); one for the lesser trochanter (thirteenth to fourteenth year); all coössified by the twentieth year in the reverse order of their appearance.

Give the muscular attachments.

The three glutei, pyriformis, two obturators, gemelli, quadratus, psoas, iliacus, two vasti, short head of biceps, pectineus, three adductors, crureus, subcrureus, gastrocnemius, plantaris, and popliteus.

The Patella. Describe the patella (Fig. 68).

It is flat, triangular, placed at the front of the lower end of the femur, and, being developed in the quadriceps tendon,

FIG. 68.-Right patella: a, anterior surface; b, posterior surface.

is probably a sesamoid bone; the convex anterior surface is roughened; the posterior surface is divided by a vertical ridge into two smooth facets for the trochlea, the outer being the