The: Vertivbral Musculature;. 181 



The iliocostalis is inserted laterally on the ribs. It receives 

 medially from the ribs a number of accessory bundles, which 

 are inserted forwards to the seventh cervical vertebra. 



The longissimus is inserted by broad fleshy bands on the posterior 

 margins of the ribs, medial to the accessory origins of the 

 iliocostalis, this portion of the muscle forming the longissimus 

 dorsi. Continuing to the neck it is inserted on the trans- 

 verse processes of the four posterior cervical vertebrae, 

 medial to the origin of the cervical portion of the serratus 

 anterior, but a number of accessory slips carry the insertion 

 forward to the transverse process of the atlas. This portion 

 is the longissimus cervicis. A separate band of fibres arising 

 chiefly from the transverse processes of the first three thoracic 

 vertebrae joins the medial, ventral portion of the splenius, 

 and forms the longissimus capitis. 

 (b) The semispinalis and multifidus. The band of muscle lying 

 between the longissimus and the middle line, is composed of 

 partly fused slips, arising for the most part by very long 

 tendons from the mammillary and transverse processes, and 

 inserted forwards on the spinous processes. It is divisible 

 into two portions, which are superficially separated by a 

 constricted area lying at the level of the last thoracic vertebra, 

 this being also the point where the muscle is fused with the 

 longissimus. The anterior portion, the semispinalis dorsi, 

 is inserted by a series of fleshy slips on the spinous process of 

 more anterior thoracic vertebra, but extends to the spinous 

 process of the third or fourth cervical vertebra. The posterior 

 portion, the multifidus, increases in size backward to the 

 sacrum, where it is continuous with the abductor caudae 

 posterior. 



An almost separate muscle, the semispinalis capitis, arises from 

 the articular processes of the five posterior cervical and the 

 transverse processes of the first four thoracic vertebrae. It 

 is inserted on the, lateral surface of the external occipital 

 protuberance. The more posterior and medial portion of 

 the muscle is composed of separate slips arising in common 

 with the longissimus capitis, two closely applied slips, how- 

 ever, at the free margin of the muscle, arising from the 

 semispinalis dorsi and the longissimus. 



A second muscle, the semispinalis cervicis, is covered by the 

 foregoing one. It arises from the articular processes of the 

 posterior cervical and first thoracic vertebrae, and is inserted 

 on the spinous processes of the cervical vertebrae, chiefly on 

 that of the epistropheus. 



(c) The intertransversarii are short muscles connecting the 

 lateral portions of the vertebrae. They are distinguishable 

 in part by their darker coloration. They increase in size 

 backwards, being most conspicuous in the lumbar region. 



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