MUSCLES OF THE BACK. 179 



scalenus posticus ; and internally with the transversalis colli. The 

 tendons of insertion are interposed between the attachments of the 

 scalenus posticus and transversalis colli. 



The transversalis colli would appear to be the continuation up- 

 wards into the neck of the longissimus dorsi ; it arises from the 

 transverse processes of the third, fourth, fifth, and sixth dorsal ver- 

 tebras, and is inserted into the posterior tubercles of the transverse 

 processes of the four or five inferior cervical vertebras. 



Relations. By its superficial surface with the levator anguli sca- 

 pulas, splenius and longissimus dorsi. By its deep surface with the 

 complexus, trachelo-mastoideus and vertebrae ; externally with the 

 musculus accessorius ad sacro-lurnbalem, and cervicalis ascendens; 

 internally with the trachelo-mastoideus and complexus. The tendons 

 of insertion of this muscle are interposed between the tendons of in- 

 sertion of the cervicalis ascendens on the outer side, and of origin of 

 the trachelo-mastoid on the inner side. 



The trachelo-mastoid is likewise a continuation upwards from the 

 longissimus dorsi. It is a very slender and delicate muscle, arising 

 from the transverse processes of the four upper dorsal, and four 

 lower cervical vertebras, and inserted into the mastoid process to 

 the inner side of the digastric fossa. 



Relations. The same as those of the preceding muscle, except- 

 ing that it is interposed between the transversalis colli and the com- 

 plexus. Its tendons of attachment are the most posterior of those 

 which are connected with the posterior tubercles of the transverse 

 processes of4he cervical vertebras. 



The complexus is a large muscle, and with the splenius forms the 

 great bulk of the back of the neck. It crosses the direction of the 

 splenius, arising from the transverse processes of the four upper 

 dorsal,* and from the transverse and articular processes of the four 

 lower cervical vertebras, and is inserted into the rough surface on 

 the occipital bone between the two curved lines, near to the occipital 

 spine. A portion of the complexus muscle is named biventer cervicis, 

 from consisting of a central tendon, with two fleshy bellies. 



Relations. By its superficial surface with the trapezius, splenius, 

 trachelo-mastoid, transversalis colli, and longissimus dorsi. By its 

 deep surface with the semi-spinalis dorsi and colli, the recti and 

 obliqui. It is separated from its fellow of the opposite side by the 

 ligamentum nuchas, and from the semi-spinalis colli by the profunda 

 cervicis artery, and princeps cervicis branch of the occipital, and 

 by the posterior cervical plexus of nerves. 



Fifth Layer. 



Dissection. The muscles of the preceding layer are to be re- 

 moved by dividing them transversely through the middle, and turn- 



* Homer describes its origin from seven dorsal and four cervical. G. 



