THE TRANSVERSO-SP1NALES AND THE SEMISPINALIS. 533 



The POSTERIOR BRANCHES OF THE LUMBAR ARTERIES divide, like Lumbar 



the foregoing, into internal and external pieces, as soon as they ar 

 reach the interval between the erector and nmltitidus spine. Each divide also 

 givs also a spinal branch to the spinal canal. 



The internal branches are small, and end in the mnltifidus spinae: inner and 



The external branches supply the erector spinae ; and offsets are outer 

 continued to the integuments with the superficial nerves. 



VEINS. The occipital veins communicate usually with the lateral Occipital 

 sinus of the skull through the mastoid foramen, and pass beneath 

 the complexus to enter the deep cervical vein. 



The deert cervical vein is of lar^e size, and besides receiving the Deep cervi- 



ca,l. V6in 



occipital veins, communicates with the other deep veins of this and plexus 

 region, forming the posterior plexus of the neck. It passes for- jjJJ|Jj; 

 wards with its artery between the transverse processes, and joins 

 the vertebral vein. 



The vertebral vein begins above the neural arch of the atlas by Beginning 

 the union of an offset leaving the spinal canal with the artery and braivein. 

 branches from the above-mentioned plexus. 



The dorsal and lumbar veins agree in their branching and Dorsal and 

 distribution with the arteries they accompany, and end in the lumbar> 

 corresponding trunks of the thoracic and abdominal wall. 



In contact with the spinous processes and laminae of the vertebras and deep 

 is a deeper set of veins (dorsal spinal), which anastomose freely v 

 together, and communicate through the ligamenta subflava with the 

 veins in the interior of the spinal canal. 



TRANSVERSO-SPINALES. Occupying the vertebral groove by the Transverse- 

 side of the spinous processes is a long muscular mass, which extends spmi 

 from the lower part of the sacrum to the axis. This is composed 

 of slips which are directed obliquely from transverse or articular arrange- 

 processes to spinous processes, and are therefore designated collec- ment> 

 lively transverso-spinales. The slips differ in length, and form 

 three layers, which are described as separate muscles, vis;., a 

 superficial stratum of loii slips, confined to the cervical and dorsal a d s t>- 



. . ,. -in ,. _,!_ v - divisions. 



regions the semispinahs ; a middle portion, with slips or inter- 

 mediate length the multijidus spines ; and a deep set of very short 

 fasciculi, present only in the thoracic region the rotatores dorsi. 

 The semispinalis and multifidus are only to be separated with 

 difficulty ; but the rotatores are more distinct, and are included in 

 the next layer. 



The SEMISPINALIS consists of slips which pass over four or five Semispinalis 

 vertebras, and it is subdivided into the following two parts, but the |j to 

 separation between them is not always distinct. 



The semispinalis dorsi is thinner than the upper part ; it arises semispinalis 

 from the transverse processes of the dorsal vertebrae from the sixth d< 

 to the tenth, and is inserted into the spines of the last two cervical and 

 the upper four dorsal vertebrae. 



The semispinalis colli (fig. 192, G) arises from the transverse and semispi- 

 processes of the upper six dorsal vertebras, and is inserted into the 

 spines of the cervical vertebrae above the last, except into the atlas, 

 The insertion into the massive spine of the axis is much the largest. 



