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Show 710 MR. F. G. PARSONS ON THE [June 16 by Faterson as derived from the dorsal divisions of the plexus the median as derived from the ventral. In all the animals dissected by Paterson, and in all that I have hitherto dissected the radial nerve came from the musculo-spiral; in this case however, the radial rose on both sides from the median, although no connection between that nerve and the dorsal roots was observed in the plexus. The arrangement of the Lumbar Plexus of the Bock-Kangaroo closely resembles that of the Cuscus described by Cunningham'; it is formed by the 2nd, 3rd, 4th, and a large part of tbe 5th lumbar nerves, the 1st lumbar being distributed to the abdominal walls. The genito-crural nerve is very small and rises from the 2nd and 3rd lumbar, whence it runs down to supply the cremaster, no crural branch being seen. The anterior crural comes from the 3rd, 4th, and 5th lumbars, and emerges from the outer surface of the psoas, soon after which it gives off the external cutaneous to supply the skin of the outer side of the thigh. As soon as tbe nerve has passed under Poupart's ligament it gives off a cutaneous branch to the skin of the front and inner side of the thigh. Soon after this a branch runs outwards to supply the sartorius, and from this a twig enters the superficial surface of the rectus femoris. The next branch is the long saphenous which comes off from the inner side of the nerve, passes superficial to the external circumflex artery, and supplies the skin on the inner side of the leg below the knee. The rest of the branches of the anterior crural pass deep to the external circumflex artery and supply the quadriceps extensor set of muscles. The obturator nerve comes from the anterior divisions of the 4th and 5th lumbar, passes to the obturator foramen, and divides into a brush of branches which supply the adductor muscles as well as the gracilis. No distinct division into superficial and deep parts was noticed. In the plexus, branches to the psoas come from the 2nd and 3rd as well as the junction between the 4th and 5th lumbar nerves. The Sacral Plexus is formed by the 5th and 6th lumbar and the greater part of the first sacral nerves, which all unite to form tbe main trunk of the great sciatic. From the junction of the 5th and 6th lumbar nerves the superior gluteal is given off, as is the case in the sacral plexus of the Cuscus; this nerve supplies the gluteus medius, minimus, and quartus. The inferior gluteal comes off in common with the small sciatic after the union of the 1st sacral with the cord formed by the 5th and 6th lumbar (lumbosacral cord) ; it supplies the gluteus maximus and the anterior part of tbe biceps. The small sciatic supplies the skin of the back of the thigh as usual. The pudic nerve is formed by the part of the 1st sacral which 1 Journ. Anat. vol. xv. p. 265. |