ROTATORES SPINJE—IXTERTRANSVERSALES 423 



5. ROTATORES SPINiE 



The rotatores spinae — named from the rotatory action which they impress 

 upon the spine — are small rhomboidal sheets, chiefly found in the thoracic region, 

 where they form a series of eleven pairs, but occasionally found also in the upper 

 lumbar and the lower cervical regions. 



Origin. — The back and upper border of the transverse process. 



Insertion. — The lower b(jrder of the lamina of the next vertebra above. 



Structure. — Sheets of parallel fibres, almost entirely fleshy, which run upwards 

 and inwards. 



Nerve-supply. — The internal divisions of the posterior primary branches. 



Action. — To rotate to the opposite side, and also to extend and laterally flex, 

 the vertebra which receiA'es its insertion. 



Relations. — Superficially, themultifidusspinse; deeply, the ligamenta subflava. 



SEVE^'TH Layer 



The seventh group consists of short vertical muscles, the interspinales and 

 intertransversales, Avhieh lie on a deep plane internal and external to the transverso- 

 spinales, and under cover of the longer vertical muscles which form the fifth layer 

 of the back. 



1. IXTERSPIXALES 



The interspinales — named from their position — are small ribbon-like muscles 

 which run vertically between the spines, especially in the cervical and lumbar 

 regions. 



Origin. — The upper surface of the spine of the vertebra, near its tip. 



Insertion. — The posterior part of the lower surface of the spine of the vertebra 

 above. 



Structure. — In the neck the bundles are attached to the two parts of the bifid 

 extremities of the spines from the axis downwards. In the lumbar region they 

 form broader bands attached to the whole length of the spines, and separated by 

 the interspinous ligaments. 



Nerve-supply. — The internal divisions of the posterior branches of the spinal 

 nerves. 



Action. — To extend the vertebra next above. 



Relations. — Behind, the spinales and complexus; internally, the interspinous 

 ligaments; externally, the multifidus si^ina'. 



Variations. — Occasionally they pass over one spine to be inserted upon the next but one. 

 The spinuhs colli, when present, may be looked upon as a still greater extension of this variation. 



2. INTERTRANSVERSALES 



The intertransversales — named from their position between the transverse 

 processes — are small vertical l)ands, also found chiefly in the cervical and lumbar 

 regions. 



In the neck (fig. 316) they are double, the anterior band connecting the anterior 

 tubercles of the transverse processes of the cervical vertebrae, and the posterior the 

 posterior tubercles. 



In the lumbar region they are also douVtle. an outer set connecting the adjacent 

 surfaces of the ends of the transverse processes, and an inner connecting the 

 accessory tubercle of one vertebra to the mannnillary tubercle of the next vertebra 

 below. A few similar pairs of muscles may also be found in the lower part of the 

 thoracic region. 



Structure. — -Fleshy, with parallel fibres. 



