THE ARTERIES. 293 
(A. intercostalis suprema), passes caudad and, dividing, sup- 
plies the first and second intercostal spaces, and then passes to 
the deep muscles of the back. The other branch divides almost 
immediately into two. One of these, A. transversa colli, 
passes laterad in front of the first rib and enters the serratus 
anterior muscle. In this it passes dorsad, giving off branches. 
to this muscle and to the levator scapula, till it reaches. 
M. rhomboideus, which it likewise supplies. The other branch 
(A. cervicalis profunda), which seems to form a continuation 
of the main artery, passes directly dorsad and leaves the 
thoracic cavity between the heads of the first and second ribs. 
Here it passes into the deep muscles of the neck; it can be 
traced in the substance of the complexus muscle as far forward 
as the atlas. 
d. Truncus thyreocervicalis (Fig. 118, 7).—The thyro- 
cervical axis (or thyroid axis) arises from the subclavian 
beneath the first rib, a short distance distad of the origin of the 
costocervical axis. It passes laterocraniad and dorsad, lying 
on the mediocranial side of the brachial plexus. A short dis- 
tance from its origin it gives offa branch, varying much in 
size, the cervicalis ascendens (Fig. 119, @), which passes 
craniad on the ventral side of the neck, supplying the sterno- 
mastoid, sternohyoid, the cervical portion of the scalenus, and 
sometimes other muscles of the neck region. Other branches 
pass from’the thyroid axis to the inner surface of the clavo- 
trapezius (Fig. 122, @) and to the ventral end of the 
pectoral muscles. At the level of the cranial border of the 
scapula the artery takes the name A. transversa scapula, or 
suprascapularis. This divides into three main branches. The 
first branch, sometimes large, sometimes small, passes to the 
lymphatic gland in the hollow of the shoulder, and to the 
adjacent muscles; it supplies the clavotrapezius, acromio- 
trapezius, levator scapule ventralis, splenius, occipitoscapularis, 
and rhomboideus. A second branch passes between the sub- 
scapularis and supraspinatus muscles, dividing into various 
branches which supply the muscles named. The third branch 
pierces the supraspinatus muscle, just craniad of the acromion 
process, and ramifies in that muscle. 
