The dorsal lumbar muscles of the cat.

Observations made in the present study of the dorsal lumbar muscles of the cat are at variance with descriptions in the available literature. The morphology of these muscles is described in detail, and a revised interpretation of this morphology is made. There are 5 muscles -- multifidus, intertransversarii mediales, lumbococcygeus, iliocostalis lumborum and longissimus lumborum. They are arranged in 5 parallel polysegmental columns and are covered by the dorsal layer of thoracolumbar fascia and the erector spinae aponeurosis. The multifidus consists of fibres connecting mamillary and spinous processes. From each mamillary process 4 sets of fasciculi arise. Each set has constant specific attachments. The intertransversarii mediales are fibres connecting accessory and mamillary process. 3 principal fasciculi arise from each accessory process and insert into particular mamillary processes at more caudal levels. The iliocostalis and longissimus arise from the ilium and from opposite surfaces of an intermuscular septum. The lumbococcygeus arises in the lumbar region from the accessory processes but inserts in the tail. Reasons for the revised nomenclature and interpretation are discussed. A specific definition of the longissimus lumborum and iliocostalis lumborum is made on the basis of their observed morphology and nerve supply. It is argued that the lumbococcygeus should be considered as the lumbar portion of sacrocaudalis dorsalis lateralis rather than part of a common muscle mass.