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omo-hyoid muscle upward. Feel the taut scalenus anticus muscle, and follow its outer border downward to the tubercle of the first rib. The artery is situated immediately behind the muscle, as it is inserted into this tubercle,

Tease the tissues from the vessel. The cords of the brachial plexus and the omo-hyoid muscle are to be retracted backward. The subclavian vein is not seen, as it lies in front of the scalenus anticus mus. cle and at a lower level. Pass the needle from before backward.

If the second portion is to be ligated, divide the scalenus anticus muscle, guarding against injuring the phrenic nerve or transversus colli artery. On the left side the thoracic duct also lies on the scalenus anticus muscle. Hug the artery with the needle to avoid the pleura.

Sometimes the vein and artery change situations; also, large branches given off from the artery may complicate the operation.

VERTEBRAL ARTERY.—Place the subject on the back, and turn the face to the opposite side.

The surface guide is the depression between the posterior border of the sterno-cleido-mastoid and the scalenus anticus muscles.

Make an incision four inches long, following the posterior border of the sterno-mastoid muscle downward to within one half inch of the clavicle. Divide the integument, platysma, and superficial fascia, and retract inward the external jugular vein. Separate the sterno-cleido-mastoid muscle from the scalenus anticus muscle. The muscle must be relaxed, by turning the face of the subject forward. The phrenic nerve, transversalis colli artery, and on the left side the thoracic duct, may be seen on the surface of the scalenus anticus. Avoid wounding these structures, and separate the scalenus anticus from the longus colli muscle. In the interspace between these muscles, the vertebral vein will first be uncovered. In the lower angle of the wound the pleura is uncovered. Retract the vein and pass the needle from the vein before backward, being mindful of the proximity to the pleura, and of the thoracic duct crossing from within outward.

The vertebral vessels vary in regard to which foramen in the transverse processes of the cervical vertebræ they enter. The arteries vary often in their origin, and hence in their ranner of reaching the intermuscular space between the longus colli and scalenus anticus muscle.

Common CAROTID ARTERY.—Place the subject on the back, with a block between the shoulders, and turn the face to the opposite side.

The surface guide is included in a line drawn from a point midway between the angle of the jaw and the mastoid process, to a point over the sternoclavicular articulation. That portion of the line below the level of the superior border of the thyroid cartilage is the surface guide.

Stand behind the shoulder.

1. Ligature over the Carotid Tubercle.- Make an incision four inches long in the line of the artery, beginning one half inch above the clavicle. Divide the integument, platysma, and superficial fascia. Retract the edges of the wound and divide the fascia at the anterior border of the sterno-mastoid muscle. Separate the muscle by means of the fingers from its attachments. Divide the fibers near the sternal origin with a probe pointed bistoury, guided on the left index-finger. Raise the head, to allow the muscle to be retracted outward. Push aside or divide between ligatures the anterior jugular vein. Divide the fascia on a director, at the outer border of the sternohyoid muscle, and retract the sterno-hyoid and sterno. thyroid muscles inward.

Feel for the carotid tubercle (the anterior tubercle of the transverse process of the sixth cervical vertebra) about two inches above the clavicle. The artery is readily felt lying upon this tubercle. Expose the carotid sheath, avoiding the recurrent laryngeal nerve and the inferior thyroid artery internally, and remembering that the left internal jugular may lie over the artery in this location. Open the sheath through its inner side directly over the artery. The pneumogastric nerve is situated behind and externally, and the internal jugular vein in front and externally, hence the needle is passed from without inward.

2. Ligature at the Level of the Cricoid Cartilage.Make an incision about four inches long in the line of the artery, having its central point at the level of the cricoid cartilage. Divide the integument, platysma, and superficial fascia. Divide the fascia at the anterior border of the sterno-mastoid muscle, and retract the muscle outward. The sterno-mastoid artery may be seen divided. Avoid the middle thyroid vein or divide it between ligatures. In the upper angle of the wound avoid injuring the superior thyroid, lingual, and facial veins, and in the lower an

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gle the anterior jugular vein. Divide the deep fascia on a director, and retract inward the sterno-thyroid and sterno-hyoid muscles.

The omo-hyoid muscle is known by its fibers extending across the carotid sheath upward and inward. On the inner side of the sheath the descendens noni nerve is seen. The omo-hyoid muscle is retracted upward or downward, or may be divided. Open the carotid sheath on its inner aspect, avoiding the descendens noni nerve. Pass the needle from without

. inward, avoiding the internal jugular vein and the pneumogastric nerve.

If the artery be ligated above the level of the cricoid cartilage, the superior thyroid artery must be avoided. If the ligature is placed below the level of the cricoid cartilage, remember that the recurrent laryngeal nerve and the inferior thyroid artery are located behind and internally.

The artery may bifurcate at a lower level than the upper border of the thyroid cartilage. The omohyoid muscle may cross the artery at a different level. The artery may give off branches, usually arising from the external carotid.

INTERNAL CAROTID ARTERY.—Place the subject as in the last operation.

The surface guide is the portion of the previously drawn line, extending from the level of the upper border of the thyroid cartilage to the point midway between the angle of the jaw and the mastoid process. Begin an incision at the upper extremity of this line, and continue it downward, following the line to the level of the body of the thyroid cartilage. Divide the integument, platysma, and superficial fascia. Divide the fascia at the anterior border of the sterno. mastoid muscle, and retract the muscle outward, raisiug the head slightly to relax the muscle. Avoid the facial, lingual, and inferior thyroid veins. Divide the deep fascia on a director, and retract upward and inward the posterior belly of the digastric and the stylo-hyoid muscles. The external carotid crossed by the hypoglossal nerve is now exposed and must be retracted inward. The internal carotid can be felt posterior and external to the external carotid.

Apply the ligature about one inch above the origin of the artery, passing the needle from without inward, to avoid the internal jugular vein and the pneumogastric nerve.

The artery may begin at different levels. The artery may be situated internal to the external carotid.

EXTERNAL CAROTID ARTERY.—Place the subject as in the previous operation. Expose the artery as described. Ligate the vessel fully an inch above the bifurcation of the common carotid. Pass the needle from without inward. Before tightening the ligature find a branch given off from the vessel, to eliminate the internal carotid. Tie any branches given off near the location of the ligature.

SUPERIOR THYROID ARTERY. — The subject is placed as in the previous operations.

Make an incision nearly three inches long, following the anterior border of the sterno-mastoid muscle, and having its middle point on a level with the upper border of the thyroid cartilage. Divide the integument, platysma, and superficial fascia. Divide the fascia along the anterior border of the sternomastoid muscle. Retract outward the sterno-mastoid

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