128 THE MUSCLES 
most of the fibres.are inserted in separate bundles by small 
tendons on the transverse processes of the vertebre, while 
some of the medial fibres unite with tendinous strands which 
become attached to the laminz and articular processes of the 
vertebra. At the region of the eighth or ninth thoracic verte- 
bra the spinalis dorsi (Fig. 69, g) begins to be separated off 
on the medial side, the separation becoming complete only 
some distance farther craniad; the longissimus dorsi then con- 
tinues into the cervical region (/”’). Bundles of fibres become 
attached in the manner above described to transverse processes 
of all the thoracic vertebra. In the cervical region (/’’) the 
muscle spreads out and becomes thinner, and bundles of fibres 
become attached to the transverse ‘processes of the cervical 
vertebre as far forward as the second. In the more cranial 
portion of its extent the muscle receives fibres having origin on 
the articular processes and laminz of the cervical and a few of 
the more cranial thoracic vertebre. 
The portion of the muscle which is inserted on the cervical 
transverse processes (/”) is sometimes distinguished as the 
longissimus cervicis; it is not well separated from the rest of 
the muscle in the cat. The longissimus capitis (Fig. 69, ¢; 
Fig. 73, g) is to be considered a differentiated cranial portion 
of this muscle. 
Relations.—Outer surface with the: following, beginning 
with the caudal end: the sartorius (Fig. 68, 7), the latissimus 
dorsi (Fig. 68, 7), the lumbodorsal fascia (Fig. 68, y), the 
serratus posterior inferior (Fig. 73, ~) and superior (Fig. 
73, 2), and the levator scapule (Fig. 73, 2). Lateral margin 
with the abdominal muscles, the iliocostal (Fig. 69, 4%), and 
the levator scapule (Fig. 73, %). Medial side with the multi- 
fidus spine (Fig. 70, @), the spinous processes of the thoracic 
vertebrae, the spinalis dorsi (Fig. 69, g), the complexus (Fig. 
69, 4), the biventer cervicis (Fig. 69, 2), and the longissimus 
capitis (Fig. 69, ¢). 
Action.—Extends the vertebral column. 
M. iliocostalis (Fig. 69, %).—This is a muscle about 14 
to 2 centimeters wide, lying on the dorsal portion of the ribs, 
laterad of the longissimus dorsi (/’). It is composed of many 
