370 THE MUSCULAR SYSTEM. 
portion of the muscle is separate, and forms the biventer cervicis, consisting of 
two fleshy bellies with an intervening tendon placed vertically in contact with the 
ligamentum nuch. The insertion of the muscle is crossed by the occipital artery. 
The complexus is covered mainly by the splenius and trachelo-mastoid muscles. 
It conceals the semispinalis colli and the muscles of the suboccipital triangle, along 
with the accompanying vessels and nerves. 
THIRD GROUP. 
These muscles are only incompletely separate from one another. The semi- 
spinalis dorsi and colli form a superficial stratum, the multifidus spine being more 
deeply placed. The more superficial muscle has the longer fibres; the fibres of the 
multifidus spine: pass over fewer vertebrae. Both muscles extend obliquely upwards 
from transverse to spinous processes. 
The semispinalis muscle extends from the loin to the axis. Its fibres are 
artificially separated into an inferior part, the semispinalis dorsi, and a superior 
part, the semispinalis colli. 
The semispinalis dorsi arises from the transverse processes of the lower six 
thoracic vertebre. It is inserted into the spinous processes of the last two cervical 
and first four thoracic vertebree. 
The semispinalis colli or cervicis arises from the transverse processes of the 
upper six thoracic vertebrae and the articular processes of the lower four cervical 
vertebre. It is inserted into the spines of the cervical vertebra from the second to 
TRAPEZIUS 
CoMPLEXUS 
Great occipital nerve 
OBLIQUUS SUPERIOR 
RECTUS CAPITIS POSTICUS MAJOR 
RECTUS CAPITIS POSTICUS MINOR 
Vertebral artery 
INSERTION OF STERNO- 
MASTOID 
SPLENIUS CAPITIS 
Suboccipital nerve 
TRACHELO-MASTOID~ Posterior arch of atlas 
OBLIQUUS INFERIOR 
Posterior primary division of second 
COMPLEXUS THROWN A 
cervical nerve 
OUTWARDS _ 
Posterior primary division of third 
Least occipital nerv , 
pit S cervical nerve 
—Deep cervical artery 
~—~ Posterior primary division of fourth 
cervical nerve 
SEMISPINALIS COLLI 
SPLENIUS CAPITIS 
TRACHELO-MASTOID: 
Fig. 273.—THE SUBOCCIPITAL TRIANGLE. 
the fifth. The semispinalis muscle occupies the vertebral furrow, and is concealed 
by the erector spinze and complexus; it covers the multifidus spine: muscle. It is 
on the same plane as the muscles of the suboccipital triangle. 
The multifidus spine differs from the previous muscle in extending from the 
sacrum to the axis, and in the shortness of its fasciculi, which pass over fewer 
vertebre to reach their insertion. It arises from the sacrum, from the sacro-iliac 
