The lumbosacral dorsal rami of the cat.

The lumbosacral dorsal rami of the cat were studied by gross dissection. The L1-6 dorsal rami form three discrete branches - lateral, intermediate and medial. The lateral branches supply the iliocostalis lumborum and become cutaneous over the back. The intermediate branches ramify in the longissimus lumborum, and are separated from the lateral branches by the lumbar intermuscular septum. The medial branches supply the multifidus and have a constant branch - the nerve to intertransversarii mediales. The L7 dorsal ramus forms only medial and intermediate branches. The S1 and S2 dorsal rami form three branches, the middle of which form the ascending sacral trunk and accessory ascending sacral trunk. The ascending sacral trunk is derived from S1 and S2, the accessory ascending sacral trunk from S2. Both nerves are the exclusive nerve supply of lumbococcygeus.