A VIEW OF THE SUPERFICIAL MUSCLES OF THE UPPER FRONT OF THE TRUNK.1. Sterno-hyoid. 2. Sterno-cleido-mastoid. 3. Sterno-thyroid. 4. Clavicular portion of the sterno-cleido-mastoid. 5. Anterior edge of the trapezius. 6. Clavicle. 7. Clavicular origin of the pectoralis major. 8. Deltoid. 9. Fold of fibres of the pectoralis major on the anterior edge of the axilla. 10. Middle of the pectoralis major. 11. The crossing and interlocking of the fibres of the external oblique of one side of the abdomen with those of the other. 12. Biceps flexor cubiti. 13. Teres major. 14. Serratus magnus anticus. 15. Superior heads of the external oblique interlocking with the serratus magnus.

The pectoralis major may now be raised from its origin, taking care to observe the nerves and arteries which penetrate its under surface.

The nerves come from the axillary, and consist of one or two branches, called the superior thoracic, Fig. 93. The arteries are branches of the superior thoracic and thoracica acromialis, Fig. 92, which arise, most frequently, by a common trunk, from the axillary artery. The pectoralis major should be

raised with a view of replacing it so as to study its relations to the axilla.

Instead of detaching the entire muscle from its origin, the student may turn down the clavicular portion at first, and dissect down to the axillary vessels and nerves, which will afford him a good view of the surgical relations of the upper part of the axillary artery. In this way, he will be able to obtain a correct idea of its depth, and what parts are necessarily involved in cutting down upon it just below the clavicle. In doing this, the following parts will be seen :

Having turned the clavicular portion of the pectoralis major down to the extent of about three inches, the costoclavicular aponeurosis will be brought into view. This is attached to the first rib, the clavicle, and the coracoid process, and is reflected downwards over the pectoralis minor.

Coming through this fascia, and close to the upper border of the pectoralis minor, will be observed the superior thoracic and thoracico-acromial arteries, Fig. 92 (11,12); the first going to the pectoralis major, and the last towards the deltoid muscle, to divide into its acromial, humeral, and thoracic branches. The acromial branch is distributed to the parts in the neighborhood of the acromion process; the humeral enters the fissure between the deltoid and pectoralis major, to be distributed principally to the former muscle; the thoracic branch goes to the latter muscle. These arteries send branches to the skin and fascia crossing the muscles.

The SUPERIOR THORACIC NERVE, which arises behind the clavicle, perforates this fascia, and accompanies the artery of the same name to the pectoralis major.

The CEPHALIC VEIN, after passing up in the groove between the deltoid and pectoralis major to near the clavicle, dips beneath the latter muscle, and passes transversely across to terminate in the axillary vein, which lies close to the thorax, Fig. 94. There are other veins in this region which open either into the cephalic, or directly into the axillary, but they are small, and have no practical importance.

Removing the fascia and areolar tissue, the upper border of the pectoralis minor below, and the subclavius muscle, Fig. 91 (, 12), above, will be seen separated by a space somewhat triangular in shape. In this space, and occupying a plane deeper than these muscles, are the axillary vein, artery, and

nerves, Figs. 93, 94. The artery is situated between the vein on its thoracic side, and the nerves on its humeral side. The artery is deeper seated than the vein, and the nerves are situated on a plane deeper than it.

In making this dissection, there is nothing destroyed which the student will have any occasion to examine afterwards; nor is it so complex as to prevent any one from making it, if he will exercise a little patience; and, when finished, he will have the satisfaction of seeing at once how the knowledge which he has acquired can be applied in practice; for he can now tell, from his own observation, which parts would have to be divided, what parts should be avoided, and how deep an incision would be required to reach the axillary artery in the upper part of its course. He has now a picture fixed in his mind, made up of several details, which sustain a certain relation to each other, and all of them to the main object in the whole group or picture. He will not be likely to forget the special anatomy of parts when their surgical relations are thus fixed in his mind. He sees, for instance, the clavicular portion of the pectoralis major, the manner in which it covers the pectoralis minor and the subclavius, with the space between them; how this space is filled up with a fascia which is perforated by small vessels and nerves; how the great arterial trunk, which is destined to supply nearly the whole of the upper extremity with arterial blood, enters the axilla; how the great venous trunk, which is required to return this blood, leaves the axilla; and how the nerves enter the same space preparatory to dividing and subdividing to go to every part of the upper extremity.

The pectoralis major having been separated from its connections, except its insertion, the pectoralis minor now comes into view.

The PECTORALIS MINOR, Fig. 91 (12), arises from the second, third, fourth, and fifth ribs, sometimes from but three, and is inserted tendinous, into the coracoid process, near its free extremity. Its tendon is connected with the coraco-brachialis and short head of the biceps, and frequently by a fibrous band with the triangular, or capsular, ligament of the shoulder joint. It forms a part of the anterior wall of the axilla, leaving a space above and below to be formed by the pecto

ralis major, the fibres of which it crosses nearly at a right angle. By observing its attachments, and the direction of its fibres, it will be seen that it can draw the scapula downwards, forwards, and inwards; or when the shoulder is carried upwards and backwards, and fixed in this position, it can elevate the ribs from which it takes its origin. Thus by placing the arm and shoulder in a proper position, both the pectoral muscles become powerful agents in expanding the upper part of the thorax.

In raising this muscle, the dissector should look for the inferior thoracic artery and nerve, Figs. 92, 93, which penetrate its under surface. The nerve is quite small, and comes from the plexus behind the muscles, and passes between the axillary artery and vein. This artery varies very much in its origin, as do all the branches of the axillary artery.

THE

A VIEW OF THE DEEPERSEATED MUSCLES ON UPPER FRONT OF THE TRUNK.-1. Cut portion of the sterno-cleido-mastoid. 2. Scalenus medius. 3. Scalenus anticus. 4. Trapezius. 5. Omo-hyoid. 6. Sterno-thyroid. 7. Sterno-hyoid. 8. Subclavius muscle. 9. First external intercostal. 10. Insertion of the pectoralis minor. 11. Cut portion of the coraco-brachialis and short head of the biceps. 12. Body of the pectoralis minor. 13. An external intercostal muscle. 14. Subscapularis. 15. Latissimus dorsi. 16. Serratus magnus.

surface of the outer part of the clavicle. It can draw the acromial extremity of the clavicle downwards and forwards, thus assisting other muscles in moving the shoulder in this direction; or when the shoulder is fixed in an opposite direction, it can assist in elevating the ribs. This muscle is placed between two layers of the costo-clavicular aponeurosis. Its relations to the axillary vessels and nerves should be observed.

The AXILLA is now fairly exposed, the whole of its anterior wall being removed. The beginner will be able to dissect and study, at least, the principal vessels and nerves, preparatory to a more thorough investigation of its contents, in his future dissections of this region.

Some of the lymphatic glands may be looked for before proceeding to dissect the vessels and nerves. There are several of these glands situated just behind the lower border of the pectoralis major, which are connected with the lymphatics of the mammary gland. Another chain is found at the border of the latissimus dorsi; and others are scattered through the axilla. Not unfrequently these glands are met with in the dissecting-room enlarged from disease.

In dissecting the vessels and nerves of the axilla, much may be done with the handle of the scalpel. They are imbedded in loose areolar tissue, which can be separated from them without much cutting. A good deal of this can be done by introducing the scissors at different points with the blades shut, and then opening them; in this way there is no danger of cutting anything, and when properly done, no occasion for breaking any of the vessels or nerves.

The AXILLARY ARTERY, Fig. 92 (9), extends from the first rib to the lower border of the tendon of the pectoralis major. It is a continuation of the subclavian. Its direction varies with the position of the arm. When the arm is dependent, it forms nearly a right angle with the subclavian; but when the arm is elevated to a right angle with the body, it forms nearly a straight line with that artery. The recollection of this fact may be of some importance in keeping the arm in a proper position, in reducing luxations of the humerus, especially if sufficient time has elapsed for adhesions to be formed.