346 THE MUSCLES AND FASCIA 



Trachelo-mastoid. It arises, by a series of tendons, from the tips of the transverse 

 processes of the upper six or seven dorsal and the last cervical vertebrae, and from 

 the articular processes of the three cervical above this. The tendons, uniting, form 

 a broad muscle, which passes obliquely upward and inward, and is inserted into 

 the innermost depression between the two curved lines of the occipital bone. This 

 muscle, about its middle, is traversed by a transverse tendinous intersection. The 

 Biventer cervicis is a small fasciculus, situated on the inner side of the preceding, 

 and in the majority of cases blended with it; it has received its name from having 

 a tendon intervening between two fleshy bellies. It is sometimes described as a 

 part of the Complexus. It arises by from two to four tendinous slips, from the 

 transverse processes of as many of the upper dorsal vertebrae, and is inserted, on 

 the inner side of the Complexus, into the superior curved line of the occipital bone. 

 Relations. The Complexus is covered by the Splenius and the Trapezius. 

 It lies on 'the Rectus capitis posticus major and minor, the Obliquus capitis 

 superior and inferior, and on the Semispinalis colli, from which it is separated by 

 the profunda cervicis artery, the princeps cervicis artery, and branches of the 

 posterior primary divisions of the cervical nerves. The Biventer cervicis is 

 separated from its fellow of the opposite side by the ligamentum nuchas. 



Fifth Layer. 



Semispinalis dorsi. Extensor coccygis. 



Semispinalis colli. Intertransversales. 



Multifidus spinas. Rectus capitis posticus major. 



Rotatores spinas. Rectus capitis posticus minor. 



Supraspinales. Obliquus capitis inferior. 



Interspinales. Obliquus capitis superior. 



Dissection. Remove the muscles of the preceding layer by dividing and turning aside the 

 Complexus ; then detach the Spinalis and Longissimus dorsi from their attachments, divide the 

 Erector spinae at its connection below to the sacral and lumbar spines, and turn it outward. 

 The muscles filling up the interval between the spinous and transverse processes are then 

 exposed. 



The Semispinalis dorsi (Fig. 214) consists of thin, narrow, fleshy fasciculi 

 interposed between tendons of considerable length. It arises by a series of small 

 tendons from the transverse processes of the lower dorsal vertebrae, from the 

 tenth or eleventh to the fifth or sixth ; and is inserted, by five or six tendons, 

 into the spinous processes of the upper four dorsal and lower two cervical vertebrae. 



The Semispinalis colli, thicker than the preceding, arises by a series of tendinous 

 and fleshy fibres from the transverse processes of the upper five or six dorsal vertebras, 

 and is inserted into the spinous processes of four cervical vertebras, from the axis to the 

 fifth cervical. The fasciculus connected with the axis is the largest, and chiefly 

 muscular in structure. 



Relations. By their superficial surface, from below upward, with the Spinalis 

 dorsi, Longissimus dorsi, Splenius, Complexus, the profunda cervicis artery, the 

 princeps cervicis artery, and the internal branches of the posterior divisions of 

 the first, second, and third cervical nerves ; by their deep surface, with the Mul- 

 tifidus spinas. 



The Multifidus spinse consists of a number of fleshy and tendinous fasciculi 

 which fill up the groove on either side of the spinous processes of the vertebras, 

 from the sacrum to the axis. In the sacral region these fasciculi arise from the 

 back of the sacrum, as low as the fourth sacral foramen, and from the aponeurosis 

 of origin of the Erector spinae ; from the inner surface of the posterior superior spine 

 of the ilium and posterior sacro-iliac ligaments ; in the lumbar regions, from the ar- 

 ticular processes ; in the dorsal region, from the transverse processes ; and in the 

 cervical region, from the articular processes of the three or four lower vertebras. 

 Each fasciculus, passing obliquely upward and inward, is inserted into the whole 

 length of the spinous process of one of the vertebras above. These fasciculi 

 vary in length : the most superficial, the longest, pass from one vertebra to the 



