Developement.— According to Bedard, the femur begins to ossify before the humerus; its ossification commences about the thirtieth day by a point for the shaft. A second point of ossification is for the inferior extremity, and this consists in a single osseous nucleus which is formed within the last month of fetal ex istence, and is situated between the two con dyles, occupying the centre of the cartilage. According to Cniveilhier this osseous nucleus appears during the last fifteen days of intra uterine life. " The constant presence," adds this author," of this osseous point in the inferior extremity of the femur is a fact of great im portance in legal medicine ; because from the knowledge of this circumstance alone, namely, that this nucleus exists in the epiphysis of the inferior extremity of the femur of a fetus, we can pronounce that fetus to have arrived at its full period." The neck of the femur is formed by an ex tension from the body. The head has a distinct point of ossification which begins to form at the end of the first year. The trochanters have each a separate point of ossification ; that of the great trochanter is formed about the third or fourth year, that of the lesser from the thir teenth to the fourteenth year. These several osseous points are united to the shaft about the period of puberty in the following order; first, the trochanter minor, next the head and trochan ter major, and lastly the inferior extremity.
In the skeleton the femur is articulated so that its inferior extremity approximates the corresponding part of the bone of the op posite side, while .the superior extremities are separated from each other to a considerable extent. One object of this oblique position of the femora has been already referred to, namely, to bring both condyles of each femur in con tact with the articular surfaces of the vertical tibiae. In women, in consequence of the more horizontal position of the neck of the femur and the greater width of the pelvis, the ob liquity is more manifest, and hence they are naturally more in-kneed than men, as from the greater projection of the internal condyle that surface alone would come in contact with the tibia if the position of the femur were vertical. The separation above is ef fected by the neck of the bone, and the ad vantage of this arrangement is to give a more favourable insertion to the muscles of rotation ; they thus acquire a lever power proportionate to the length of the neck, a fact which is abundantly manifest by comparing the relative powers of rotation in the shoulder and hip joints; in the former these motions are more extensive, because, from the peculiar form of the joint, the obstacles to extent of motion are fewer; in the latter they are effected with greater power at a less expense of muscular force.
In comparing the femur of man with that of the lower mammalia, we notice the imperfect devclopement or the non-developement of the cervix in the latter, the head in some being placed nearly vertically over the shaft of the bone, and also the small size of the trochanters, and the magnitude of the trochanter major in some classes. The curved form of the shaft of the femur is much less in the lower mammalia than in man; in some the femur is perfectly straight, and as a consequence the Linea aspera or spine is indistinctly marked. The propor tionate length of the femur to the other bones of the inferior extremity differs also : in man it exceeds that of the tibia; in the inferior mammalia, although in most cases the strongest bone, the femur is shorter than the tibia, and shorter even than the foot, although longer than each segment of this portion of the limb. The trochlea in the inferior extremity is deeper, and the transverse dimensions of the condyles are less than in man.
Patella, (rotula, knee-pan, os sesamoideum maximum, Bertin ; Fr. la rotule ; Germ. die Knicseheibe). This bone, although belonging to the class of sesamoid bones, is yet so fully developed in the adult human subject, and is so essential to the integrity of the knee-joint, that it is usual to examine its anatomical characters along with those of the other bones of the in ferior extremity. Its developement in the tendon of the rectus femoris leads to its being classed among the sesamoid bones.
The patella is of a triangular form, the apex being directed downwards and the base up wards; the former is connected with the tibia by the continued tendon of the rectus, under the name of ligamentum patellae; the tendon of the rectus and the tendinous expansions of the triceps extensor are inserted into the base, which expansions are likewise implanted into the margins of the bone, so that the whole circumference and anterior surface of the pa tella are invested with tendinous fibres.
The anterior surface of the patella is very slightly convex. and exhibits a fibrous ap pearance produced by vertical and parallel fibres, with narrow fissures between, into which the fibrous expansion which invests this surface is implanted. The posterior surface is articular and adapted to the trochlea of the femur. A vertical ridge, which inclines a little outwards in its descent, divides this sur face into two lateral portions; each of these por tions is a concave articular facet for adaptation to the anterior part of each condyle of the femur, and consequently there is between these surfaces the same inequality which exists be tween the condyles. In the recent condition these surfaces are covered by a soft and very elastic cartilage.