OF THE BACK. 347 



third or fourth above ; those next in order pass from one vertebra to the second or 

 third above ; whilst the deepest connect two contiguous vertebrae. 



Relations. By its superficial surface, with the Longissimus dorsi, Spinalis 

 dorsi, Semispinalis dorsi, and Semispinalis colli ; by its deep surface, with the 

 laminae and spinous processes of the vertebrae, and with the Rotatores spinae in 

 the dorsal region. 



The Rotatores spinae are found only in the dorsal region of the spine, beneath 

 the Multifidus spinae ; they are eleven in number on each side. Each muscle 

 is small and somewhat quadrilateral in form ; it arises from the upper and back 

 part of the transverse process, and is inserted into the lower border and outer 

 surface of the lamina of the vertebra above, the fibres extending as far inward as 

 the root of the spinous process. The first is found between the first and second 

 dorsal ; the last, between the eleventh and twelfth. Sometimes the number of 

 these muscles is diminished by the absence of one or more from the upper or lower 

 end. 



The Supraspinales consist of a series of fleshy bands which lie on the spinous 

 processes in the cervical region of the spine. 



The Interspinales are short muscular fasciculi, placed in pairs between the 

 spinous processes of the contiguous vertebrae, one on each side of the interspinous 

 ligament. In the cervical region they are most distinct, and consist of six pairs, 

 the first being situated between the axis and third vertebra, and the last between 

 the last cervical and the first dorsal. They are small narrow bundles, attached, 

 above and below, to the apices of the spinous processes. In the dorsal region 

 they are found between the first and second vertebrae, and occasionally between 

 the second and third ; and below, between the eleventh and twelfth. In the 

 lumbar region there are four pairs of these muscles in the intervals between the 

 five lumbar vertebrae. There is also occasionally one in the interspinous space, 

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

 sacrum. 



The Extensor coccygis is a slender muscular fasciculus, occasionally present, 

 which extends over the lower part of the posterior surface of the sacrum and 

 coccyx. It arises by tendinous fibres from the last bone of the sacrum or first 

 piece of the coccyx, and passes downward to be inserted into the lower part of 

 the coccyx. It is a rudiment of the Extensor muscle of the caudal vertebrae of 

 the lower animals. 



The Intertransversales are small muscles placed between the transverse proc- 

 esses of the vertebrae. In the cervical region they are most developed, consisting 

 of rounded muscular and tendinous fasciculi, which are placed in pairs, passing 

 between the anterior and the posterior tubercles of the transverse processes of two 

 contiguous vertebrae, separated from one another by the anterior division of the 

 cervical nerve, which lies in the groove between them. In this region there are 

 seven pairs of these muscles, the first pair being between the atlas and axis, and 

 the last pair between the seventh cervical and first dorsal vertebrae. In the dorsal 

 region they are least developed, consisting chiefly of rounded tendinous cords in the 

 intertransverse spaces of the upper dorsal vertebrae ; but between the transverse 

 processes of the lower three dorsal vertebras, and between the transverse processes 

 of the last dorsal and the first lumbar, they are muscular in structure. In the lum- 

 bar region they are arranged in pairs, on either side of the spine, one set occupy- 

 ing the entire interspace between the transverse processes of the lumbar vertebras, 

 the intertransversales laterales ; the other set, intertr cm sver sales mediales, passing 

 from the accessory process of one vertebra to the mammillary process of the next. 



The Rectus capitis posticus major arises by a pointed tendinous origin from the 

 spinous process of the axis, and, becoming broader as it ascends, is inserted into 

 the inferior curved line of the occipital bone and the surface of bone immediately 

 below it. As the muscles of the two sides pass upward and outward, they leave 

 between them a triangular space, in which are seen the Recti capitis postici 

 minores muscles. 



