Brain, behavior and evolution
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The dorsal and ventral vertebral muscles of the back and the tail of the albino Norway rat are described and discussed. These muscles were analyzed because they are undoubtably used during the sexual posturing, lordosis, of the female rat, as well as participating in a variety of other behaviors. The muscles are described by region (thoracic-lumbar or sacrocaudal), and the classifications of Vallois are followed where possible. ⋯ The innervation of the lumbar transversospinalis muscles by the medial branches and of lateral longissimus by the lateral branches of the dorsal rami of the spinal nerves was traced and confirmed by electrical stimulation of the nerve branches. The innervation of medial longissimus is also described. Additionally, movements of the vertebral column produced by direct unilateral or bilateral muscle stimulation were observed for a number of the muscles.