The develoment of the human lower limb is observed in 3 human (6, 9 and 9.5 mm long) embryos.
The lower limb bud projects succeeding upper limb in Streeter's horizon XIII stage. In the next horizon XIV there is no differentiation among the mesenchym of the limb. First in the horizon XV, to the younger half of which stage belongs our 6 mm long embryo, the axial part at the end of the lumbosacral nerve plexus differentiates in the same manner as in the upper limb. This. differentiation may be called pre-cartilageous (Fig. 1, 2, 3, P1. 1) In this stage the sacral part is projecting into the limb mesenchym, while the lumbar part not yet.
In the next horizon XVI stage, to which belongs our 9 mm. long embryo, there is pre-cartilageous femur and leg, while pelvis and peripheral part are yet mesenchymal. The outlines of the pre-cartilageous scelet are not definite. From the lumbosacral plexus of this embryo project n. femoralis, obturatorius, tibialis and fibularis communis very thick in the lower limb, especially long is the n. tibialis among them, which reaches the foot region and divides into plantaris medialis and lateralis. N. fibularis communis divides also into superficialis and profundus, among which the former is very short. Besides these 4 principal nerves there arise cutaneous branches as iliohypogastric, ilioinguinal, genitofemoral, fibular cutaneous femoris, which are very short, but from their relations to the nerve plexus on the one side and to the body regions on the other, they can be defined.
As for the arterial branches a. axis and ilica externa are observed in this embryo, while in the earlier stage ilica externa not yet
In the next to the horizonXVII belonging embryo there appear definite cartilageous scelet, d.i. ilium, pubis, ischii, femur, tibia and fibula, 3 former among them are rather pre-cartilageous. Besides these are the dense mesenchymal tarsal part and about 5 finger rays observed. In the upper limb there are 5 pre-catilageous carpal centers in this embryo, while in the tarsal part of the lower limb no such center.
For the lumbosacral plexus the anterior rami of 8 spinal nerves from L₁; to S₃ are contributed, from this plexus outgoing nerves which are nominated in the former stage are definite. The thick femoral, obturator, tibial and common fibular nerves go through the pre-muscle tissue, which are histologically from the axial sceleton on the one side and subcutaneous tissue on the other discernible. Such pre-muscle tissue is as a muscle group, not as individual muscles, to be observed. For example n. femoralis go through extensor pre-muscle tissue and its prolongation reaches the surface near foot region, which may be destined as n. saphenus.
As in 9 mm.long, so in this 9.5 mm long embryo are axial and external iliac arteries visible, which, are more thick and straight, and moreover in this stage the capillary nets in the foot -region is well developed.
The veins of these 3 embryos are almost the same. The so-called Randvene or primitive fibular vein is always in the same manner visible, which cranial end makes a net, while caudal extremity continues to the posterior cardinal vein. Cranial to this continuation comes out in 9.5 mm long embryo the femoral vein, which does not go out in the younger specimens, although in 9 mm long one its sprout can be observed.

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