The nutritious foramen of the femur is found either upon, or on one side of, the linea aspera.
The direction of the canal is upwards towards the head of the femur.
The iVerior extremity of the femur is much more considerable than the superior. We no tice upon it two articular processes of large size, united in front, but separated by a deep depression posteriorly. These processes are the external and internal condyles; at the point of union of these two condyles in front, we ob serve a transversely concave surface, which ex tends for a little distance upwards upon the anterior surface of the bone ; this is the trochlea of the femur, on which the patella moves. The deep notch which separates the condyles poste riorly is denominated the intereontlyloid notch.
Each condyle is ovoidal in its outline and convex. The external condyle is placed di rectly under the external part of the femur; it projects more forwards than the internal con dyle; its antero-posterior diameter is less than that of the internal condyle, but its trans verse is greater. On the other hand, the in ternal eondyle projects inwards out of the plane of the internal surface of the bone; its posterior extremity extends much further backwards than that of the external, and if the bone be placed at right angles with a plane surface, it will be seen that this condyle alone touches that surface, a circumstance which arises from the internal condyle project ing downwards more than the external. It is also worthy of notice, as resulting from this conformation of the internal condyle, that in order to bring both condyles in contact with a plane surface, the bone must be made to in cline with the inferior extremity inwards. Above the posterior extremity of each condyle there is a depression for the insertion of the two heads of the gastrocnemius muscle.
The external surface of the external condyle is continuous with the outer surface of the shaft; it is rough and convex, and is called by some anatomists the external tuberosity. At its posterior part there is a prominent tubercle to which the external lateral ligament is attached, and below and a little posterior to this is a de pression into which the tendon of the popliteus is inserted. The internal surface of this con dyle forms the outer wall of the depression which separates the condyles behind ; it is concave, and has the anterior crucial ligament inserted into it. The inner wall of this notch
is formed by the external surface of the in ternal eondyle, which is likewise concave, and into it are implanted the fibres of the pos terior crucial ligament. The internal surface of this condyle, or the internal tuberosity, is rough, much more convex than the external tuberosity; the internal lateral ligament and tendon of the adductor magnus are inserted into it. Both the tuberosities are perforated by a number of minute foramina for the trans mission of vessels to the cancellated texture.
Structure.—A vertical section of the femur demonstrates its structure to be the same as that of all the long bones, composed of can cellated texture at the extremities and com pact in the shaft, which is bored by a cylin drical canal. Posteriorly the compact tissue is of great density and hardness, especially where it forms the linen aspera or spine of the bone. When the section of the femur is made so as to divide the neck vertically in its long axis into two equal portions, we observe how ad mirably the arrangement of the osseous texture in this part is adapted to the function which it has to perform. The head is entirely composed of reticular texture surrounded by a thin cortex ; this cortex gradually increases in thickness on the upper surface of the neck till it reaches the great trochanter. On the inferior surface of the neck, however, the compact tissue, although thin near the head, becomes very much in creased in thickness as it curves downwards and outwards to the lesser trochanter. We observe, moreover, that although the principal portion of the head and neck are composed of reticular texture, in certain parts this texture is more loose than in others. From the upper part of the head to the thick part of the compact tissue on the inferior surface of the neck, a series of parallel fibres proceed in an oblique course, and closely applied to one another; these fibres receive and transmit the weight to the arch of the neck.' Again, the reticular texture is loose and rare, external to these fibres and in all the inferior part of the head of the bone where no stress is laid upon the hone.