FEMUR (Lat., thigh). The thigh-bone. In general terms, it consists of a shaft, very slightly curved, and two extremities. The upper ex tremity bears two projections. called the greater and lesser trochanters, for the attachment of muscles, and a short neck, nearly at right angles to the shaft, terminated by a hemispherical head, which, being received into a cavity of the pelvis called the acetabulum, forms the hip-joint—a ball-and-socket joint. The lower extremity of the femur has on each side an enlargement called a comlyle, or knuckle. The articular surface of the condyles is hemicylindrical, as also is the somewhat depressed space between them, called the trochela, and with the large bone of the leg, called the tibia, forms the hip-joint—a hinge joint. The femur is attached to the pelvis by two ligaments—a capsular ligament. which Meioses the head and neck, and the liga mentum tcres, a sharp ligament which joins the head with the bottom of the neetabu lum. It is attached to the tibia by several ligaments, placed in different positions, to com bine strength with freedom of motion, the most important of which are the lateral ligaments and the crucial ligaments. The crucial ligaments
cross from one member of the joint to the other in oblique directions. Powerful extensor and flexor muscles, besides performing their ordinary functions, aid in keeping the in opposition. The femur has a wide range of distribution in the animal kingdom, and is not the exclusive property of warm-blooded animals. In man it is the strongest, longest, and largest bone. In the whale it is only rudimentary. In fishes it is not represented; but has a varying importance in mamnia)s, birds, reptiles, and amphibians. It is a short bone in the ruminants and the horse family: In the tortoises the curve is consider able, while it is almost straight in carnivora, bats, etc. In many reptiles it is slightly rudi menta•y. For illustrations. see SKELETON.