_c._ =Truncus costocervicalis= (Fig. 118, _g_).--The costocervical axis arises from the subclavian opposite the first rib, passes craniodorsad, and divides almost at once into two branches. The smaller one of these, the =superior intercostal= (=A. intercostalis suprema=), passes caudad and, dividing, supplies 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 scapulæ, 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 thyrocervicalis= (Fig. 118, _j_).--The thyrocervical 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 distance from its origin it gives off a branch, varying much in size, the =cervicalis ascendens= (Fig. 119, _d_), which passes craniad on the ventral side of the neck, supplying the sternomastoid, 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 clavotrapezius (Fig. 122, _a_) 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 scapulæ=, 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, acromiotrapezius, levator scapulæ ventralis, splenius, occipitoscapularis, and rhomboideus. A second branch passes between the subscapularis 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. _e._ =A. axillaris= (Fig. 122, _g_).--The axillary artery is the continuation of the subclavian laterad of the first rib. It lies caudad of the brachial plexus and parallel to it. It sends off the following branches: 1. =A. thoracica anterior= (Fig. 122, _h_).--The anterior thoracic is a slender artery which leaves the ventral side of the axillary opposite the first rib and passes caudomediad, to supply the medial ends of the pectoral muscles (_g_).