ZUb MUSCLES OP THE BACK. 



dorsal vertebrae, and are inserted into the spinous process of the axis. 

 From its analogy to the spinalis dorsi this muscle has been named 

 spinalis colli. It is sometimes wanting. 



The INTERSPINALES are small muscular slips arranged in pairs and 

 situated between the spinous processes of the vertebrae. In the cer- 

 vical region there are six pairs of these muscles, the first being placed 

 between the axis and third vertebra, and the sixth between the 

 last cervical and first dorsal. In the dorsal region, rudiments of these 

 muscles are occasionally met with between the upper and lower verte- 

 brae, but are absent in the rest. In the lumbar region there are six 

 pairs of interspinales, the first pair occupying the interspinous space 

 between the last dorsal and first lumbar vertebra, and the last the 

 space between the fifth lumbar and sacrum. They are thin and 

 imperfectly developed. Rudimentary interspinales are occasionally 

 met with between the lower part of the sacrum and the coccyx ; these 

 are the analogues of the caudal muscles of brutes ; in man they have 

 been named collectively the extensor coccygis. 



The INTERTR ANSVERSALES are small quadrilateral muscles situated 

 between the transverse processes of the vertebrae. In the cervical 

 region they are arranged in pairs corresponding with the double con- 

 formation of the transverse processes, the vertebral artery and anterior 

 division of the cervical nerves lying between them. The rectus an- 

 ticus minor and rectus lateralis represent the intertransversales be- 

 tween the atlas and cranium. In the dorsal region the anterior inter- 

 transversales are represented by the intercostal muscles, while the pos- 

 terior are mere tendinous bands, muscular only between the first and 

 last vertebrae. In the lumbar region, the anterior intertransversales 

 are thin and occupy only part of the space between the transverse 

 processes. Analogues of posterior intertransversales exist in the form 

 of small muscular fasciculi (interobliqui) extended between the rudi- 

 mentary posterior transverse processes of the lumbar vertebrae. 



With regard to the origin and insertion of the muscles of the back, 

 the student should be informed, that no regularity attends their at- 

 tachments. At the best, a knowledge of their exact connections, even 

 were it possible to retain it, would be but a barren information, if not 

 absolutely injurious, as tending to exclude more valuable learning. I 

 have therefore endeavoured to arrange a plan, by which they may be 

 more easily recollected, by placing them in a tabular form (p. 208), 

 that the student may see, at a single glance, the origin and insertion 

 of each, and compare the natural grouping and similarity of attach- 

 ments of the various layers. In this manner also their actions will be 

 better comprehended, and learnt with greater facility. 



Actions. The upper fibres of the trapezius draw the shoulder 

 upwards and backwards ; the middle fibres, directly backwards ; and 

 the lower, downwards and backwards. The lower fibres also act by 

 producing rotation of the scapula upon the chest. If the shoulder be 

 fixed the upper fibres will flex the spine towards the corresponding 

 side. The latissimus dorsi is a muscle of the ann, drawing it back- 



