Os, (from the same). Thigh bone; anche os. In the thigh there is only one bone; it is the largest and strongest of those which are cylindrical. On its outside, near the neck, is a large tuberosity, the trochanter major, rotator major, rotator natis; and a lesser one, on the inside, the trochanter minor,"rotator minor. The posterior concave surface of this bone hath a ridge rising in its middle, called the linea aspera, divided below into two. The inferior extremity of this bone is formed into two condyles, between which a considerable cavity is found, especially at the posterior part: these are contiguous forwards, but at a distance backwards. The os femoris is articulated to the acetabulum by enarthrosis; to the tibia and the patella by ginglymus. Winslow observes, that all the processes from this bone are cartilaginous in new born children.
Though the thigh bone supports the whole body it is by no means, in appearance, advantageously constructed, since it bends inward towards the knee, and outwards at the top; but the former was necessary to avoid a rotatory motion of the leg, and the latter to form a sufficient space for the organs at the bottom of the abdomen.
As the great trochanter passes off at nearly a right angle to enlarge the cavity just mentioned, any shock of the trunk renders it liable to fracture, and this is often mistaken for luxation; an error with difficulty corrected, as the muscles are so thick and so numerous in this part.