In Birds the radius and ulna are distinct throughout, but do not admit of motion between them; they are fixed in a state intermediate be tween pronation and supination.
The Iland.—The third division of the upper extremity is the hand : for the description of the bones which compose it, we refer to the article !LAND.
Inferior extremity.—The bones which form the skeleton of the inferior or pelvic extremity are the femur, tibia, fibula, and the bones of the foot, occupying subdivisions of this mem her, which correspond to the arm, forearm, and hand in the pectoral extremity.
Femur ( thigh-bonc, os lemoris v. cruris, os rasa.. Fr. os de la cuissc, femur. Germ. tics -hcnkelkin.) This is the largest and longest bone of the skeleton; it constitutes the upper part of the inferior extremity, and is articulated with the pelvis above and the tibia inferiorly. The femur exhibits very obviously the characteristic marks of the class of long bones in its elonga ted and cylindrical shaft, and its swollen extre mities.
The superior extremity of the femur consists of a spherical head, connected to the shaft of the bone by a neck. The head is very regu larly spheroidal, being nearly two-thirds of a sphere ; it is limited towards the neck by a waving line which passes all round, and corre sponds to the margin of the acetabulum. The whole head of the femur is incrusted in the recent state with articular cartilage, excepting at one point, where there is a depression or pit, varying in depth in different subjects. The precise situation of this depression is just infe rior and posterior to the point at which the axis of the head of the femur would pass out : into this depression the ligamentum teres is in serted.
From the head of the femur is prolonged outwards and downwards to the upper end of the shaft the neck (cervix v. collum femoris). This portion of bone, cylindrical where it is connected to the head, gradually expands as it proceeds outwards, and is flattened in front and behind. That portion of the neck of the femur which is connected with the shaft may be called its base ; here we observe two lines, by which the demarcation between the neck and shaft is indicated ; one of these lines is anterior, being simply a rough line extending from the great trochanter obliquely downwards, inwards, and slightly backwards to the lesser trochanter, and thence called the anterior inter trochanterie line, into which the capsular liga ment of the hip-joint is inserted; the other line may be more correctly designated a prominent ridge ; it is situated at the posterior part of the base of the neck, and extended also between the troclianters, the posterior intcr-trochontcric line. The anterior surface of the neck of the femur is for the most part plane, but slightly concave just external to the line of junction of the head. The superior surface of the neck is concave, being limited on the outside by the great tro chanter; the posterior surface is likewise con cave, being, as it were, hollowed from within outwards. The inferior surface is slightly con
cave from above downwards, but rounded from before backwards : this surface inclines down wards and outwards, and at its termination is connected with the trochanter minor behind, and the inner side of the shaft of the bone in front ; in length it exceeds all the rest ; the su perior surface is the shortest, and the posterior is longer than the anterior. On all the surfaces of the neck we observe numerous foramina for the transmission of vessels into the substance of the bone ; these foramina are largest and most numerous on the superior surface.
At the superior angle of the base of the neck of the femur, and at the upper and outer part of the shaft of the bone, we observe a large and thick process, the trochantcr major, (from .reozaw, roto,) proccssus exterior Jemoris ; it is a prolongation upwards of the shaft of the bone, but its most elevated point is below the level of the head of the bone, corresponding to the upper part of the line of junction of the head with the neck. "This eminence," says Cruveilhier, " whose size is considerable, and which makes a very manifest prominence under the skin, ought to be studied with care in its relations as to its relative position ; first, with the crista ilia, beyond which it projects exter nally ; secondly, with the external condyle of the femur; thirdly, with the malleolus exter nus, because these relations are constantly va luable guides, as well in the diagnosis as in the reduction, of the luxations of the femur and of the fractures of the neck or shaft of the bone." The external surface of the great trochanter is convex and rough, and the tendon of the glutceus maximns muscle covers it in the recent condition ; this surface is terminated below by a projecting line, into which is inserted the upper extremity of the vastus externus muscle. The internal surface is of much less extent : it is placed at right angles with the superior sur face of the neck of the bone, and at its posterior part it is excavated so as to form a deep pit or depression, the digital cavity orfossa trochante rice, into which are inserted the tendon of the pyriformis, the gemelli, and the obturatores internus and externus. The anterior edge is thick and irregular; the glutcei medius and minimus are inserted into it, the former into its inferior, the latter into its superior part. Superiorly the trochanter forms a thin edge, more or less pointed, into the interior half of which the glutceus minimus is inserted, and into its posterior or pointed portion the glutceus medius; it may in general be observed, that the size of this pointed part of the superior edge of the great trochanter is proportionate to the developement of the glutceus medius mus cle. The posterior edge is convex and thick, and gives attachment to the quadrates femoris muscle.