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to the Infraspinatous muscle, besides some filaments to the shoulder-joint and scapula.

The Nerve to the Subclavius (n. subclavius) is a small filament, which arises from the point of junction of the fifth and sixth cervical nerves; it descends to the muscle in front of the third part of the subclavian artery and the lower trunk of the plexus, and is usually connected by a filament with the phrenic nerve.

The Long Thoracic Nerve (n. thoracalis longus; external respiratory nerve of Bell; posterior thoracic nerve) (Fig. 816) supplies the Serratus anterior. It usually arises by three roots from the fifth, sixth, and seventh cervical nerves; but the root from the seventh nerve may be absent. The roots from the fifth and sixth nerves pierce the Scalenus medius, while that from the seventh passes in front of the muscle. The nerve descends behind the brachial plexus and the axillary vessels, resting on the outer surface of the Serratus anterior. It extends along the side of the thorax to the lower border of that muscle, supplying filaments to each of its digitations.

The branches for the Longus colli and Scaleni arise from the lower four cervical nerves at their exit from the intervertebral foramina.

Infraclavicular Branches.—The infraclavicular branches are derived from the three cords of the brachial plexus, but the fasciculi of the nerves may be traced through the plexus to the spinal nerves from which they originate. They are as follows:

Lateral cord……	Musculocutaneous…………	5, 6, 7 C.
	Lateral anterior thoracic……	5, 6, 7 C.
	Lateral head of median……..	6, 7 C.
Medial cord……	Medial anterior thoracic
	Medial antibrachial cutaneous
	Medial brachial cutaneous….	8 C, 1 T.
	Ulnar
	Medial head of median
Posterior cord…	Upper subscapular…………	5, 6 C.
	Lower subscapular…………	5, 6 C.
	Thoracodorsal..……………	5, 6, 7 C.
	Axillary……………………	5, 6 C.
	Radial………………………	6, 7, 8 C, 1 T.

The Anterior Thoracic Nerves (nn. thoracales anteriores) (Fig. 816) supply the Pectorales major and minor.

The lateral anterior thoracic (fasciculus lateralis) the larger of the two, arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves. It passes across the axillary artery and vein, pierces the coracoclavicular fascia, and is distributed to the deep surface of the Pectoralis major. It sends a filament to join the medial anterior thoracic and form with it a loop in front of the first part of the axillary artery.

The medial anterior thoracic (fasciculus medialis) arises from the medial cord of the plexus and through it from the eighth cervical and first thoracic. It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the lateral nerve. It then enters the deep surface of the Pectoralis minor, where it divides into a number of branches, which supply the muscle. Two or three branches pierce the muscle and end in the Pectoralis major.

The Subscapular Nerves (nn. subscapulares), two in number, spring from the posterior cord of the plexus and through it from the fifth and sixth cervical nerves.

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