The _shaft_ of the femur is enlarged at the extremities and is slightly curved forward, the concavity being strengthened at the back by a longitudinal ridge, the _linea aspera_, along part of which the gluteus maximus muscle is attached. The _head_, which is covered with cartilage, except for an oval depression for the attachment of the ligamentum teres, one of the ligaments of the hip-joint, and which articulates with the hollow of the acetabulum in the os innominatum, projects considerably upward, inward, and forward from the shaft, the _neck_ varying much in length and angle. It is generally more horizontal in women than in men and in rickets the great weight on the softened bone tends to press the head down, causing the deformity known as “_coxa vera_”, in which the neck is almost horizontal. Extending upward, outward, and backward from the shaft at the base of the neck, about three-quarters of an inch lower than the head and about on a level with the acetabulum and the spine of the os pubis, is the _greater trochanter_. This large, irregular prominence and the smaller one of the _lesser trochanter_, which is at the lower part of the base of the neck posteriorly, are for the attachment of muscles and to assist in rotating the bone. The lower extremity of the femur is larger than the upper and is flat from before backward. Between its two large eminences, the external and internal _condyles_, is a smooth depression in front, the _trochlear surface_, for articulation with the patella. The external condyle is more prominent in front, the internal inferiorly, the latter being the longer of the two by about half an inch. The _epiphysis_ at the lower end of the femur is the only one in which ossification has begun at birth. Therefore, if ossification is found there, the child is known to have arrived at full term. [Illustration: FIG. 74.--Bones of the lower extremity. (Toldt.)] So many large muscles are attached to the femur that the shaft cannot be detected in the living unless the person is very thin and poorly developed. The outer surface of the greater trochanter, however, and the condyles can be felt. A string stretched from the anterior superior spine of the ilium to the tuberosity of the ischium passes in the middle just over the upper edge of the greater trochanter. The line thus drawn is known as _Nélaton’s line_ and is of considerable importance in many conditions of the hip. Thus, if the hip is dislocated, the trochanter will be thrown above _Nélaton’s line_, and in osteomalacia the pelvis sinks and the trochanter is again above the line.