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Tuscle. It crosses forwards, superficial to the occipital and internal and rotid arteries, immediately below the origin of the superior sterno-mastoid the first-mentioned vessel. The vagus nerve descends vertically, within I sheath, behind and between the carotid vessels and the internal jugular ; must be taken not to include it when ligaturing the common carotid il jugular. Surgically, the accessory is the most important nerve in the ciangle; it enters the substance of the sterno-mastoid muscle 14 in. below

the mastoid process. A portion of the nerve is resected in the treatment odic wry-neck, and it is always exposed in the removal of the medial

deep cervical glands. The course of the nerve may be mapped out 1 surface by drawing a line from a point midway between the tip of joid process and the angle of the mandible to a little above the middle sterior border of the sterno-mastoid muscle, and thence across the posterior to the anterior border of the trapezius, beneath which it passes at the level venth cervical spine. The deeper guides to the nerve are the posterior belly igastric, and the internal jugular vein which it crosses, very obliquely, from ownwards and backwards below and in front of the transverse process of s (felt as a distinct bony landmark midway between the tip of the mastoid e angle of the mandible). The cervical sympathetic lies in the posterior

the vascular compartment of the neck, and may be reached by an incision he posterior border of the sterno-mastoid: the anterior surfaces of the roots transverse processes of the vertebræ are the deep guides to the nerve. e cervical plexus, which lies deep to the superior half of the sterno-mastoid he levator scapulæ and scalenus medius muscles, may be exposed through an n along the posterior border of the upper half of the sterno-mastoid muscle. brenic nerve, the most important branch of the cervical plexus, arises one inch the carotid tubercle and descends almost vertically upon the scalenus anterior; verlapped by the lateral margin of the internal jugular vein. Although frely exposed by the surgeon in removing the lower medial group of deep cal glands, the phrenic nerve is protected from injury by being covered by revertebral fascia. he muscular or lower carotid triangle is an important triangular interular space bounded by the anterior border of the sterno-mastoid, the anterior

of the omo-hyoid, and the sterno-hyoid. Behind this space, and forming, as ere, its floor, is a still deeper space bounded by the longus colli and scalenus rior muscles. It may with advantage be termed the prevertebral intermuscular ngle, or, from the fact that it contains the vertebral artery, it may be termed vertebral arterial triangle. At its apex is the prominent anterior tubercle of transverse process of the sixth cervical vertebra. By making an incision along anterior border of the left sterno-mastoid muscle, and passing through this ngle, the surgeon reaches, in order from before backwards, the internal jugular n, the common carotid artery, the vagus, the thoracic duct, the middle cervical aglion of the sympathetic, the inferior thyreoid artery, the vertebral vessels, : recurrent nerve, and the csophagus. The most important bony landmark in is triangle is the prominent anterior tubercle of the transverse process of the ath cervical vertebra. The common carotid artery may be compressed against is tubercle, which is therefore termed the “carotid tubercle.It is the most aportant guide to the vertebral artery, which enters the foramen in the transverse rocess of the sixth cervical vertebra.

The cervical portion of the csophagus, which begins at the level of the cricoid urtilage, descends behind, and a little to the left of, the trachea. To expose it, the urgeon, after passing through the above-mentioned muscular triangle, divides he pretracheal fascia, and passes between the trachea and the carotid sheath down o the longus colli muscle medial to the inferior thyreoid artery and vertebral sessels. The lower pole of the corresponding lobe of the thyreoid gland is retracted medially along with the trachea. The oesophagus lies in the loose cellular tissue in front of the prevertebral fascia ; hence it can be mobilised sufficiently to admit of its being brought to the surface. The cesophagus may also be exposed through an incision in the median plane, the trachea, which is freely movable, being displaced to the right side. In opening the oesophagus care must be taken not to injure the recurrent nerve, which ascends in the groove between it and the trachea, and also that the loose submucous cellular interval must not be mistaken for the lumen of the tube. The recurrent nerve must be avoided also in operations connected with the thyreoid gland; it is most liable to be injured during the application of a ligature to the inferior thyreoid artery, which arches medially in front of the nerve to reach the posterior surface of the gland.

THE THORACIC DUCT.

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The thoracic duct, after entering the root of the neck between the esophagus and the pleura, ascends to about an inch above the clavicle. At this level it arches laterally behind the lower part of the carotid sheath in front of the vertebral vessels Great care must therefore be taken not to injure the duct in removing the lymph glands which lie in the loose cellular tissue behind the inferior part of the internal jugular vein, between it and the vertebral vein at the medial border of the scalenus anterior. In addition to those glands a few small lymph glands lie adjacent to the lateral aspects of the cervical portions of the trachea and oesophagus. They receive their afferent vessels from the larynx, trachea, æsophagus, and thyreoid gland.

POSTERIOR TRIANGLE.

The roof of the posterior triangle is formed by the general envelope of deep cervical fascia, while the fascia which covers the muscles forming its floor, as well! as that covering the brachial nerve trunks and the subclavian artery, is a lateral continuation of the prevertebral fascia. The lateral deep cervical and supraclavicular lymph glands are embedded in the cellular tissue between these two layers of fascia. În removing these glands, every endeavour should be made to preserve the motor nerves. The accessory nerve, after entering the posterior triangle at the junction of the superior and middle thirds of the posterior border of the sterno-mastoid muscle, crosses the triangle superficially, and parallel to the levator scapulæ. It leaves the triangle by passing under cover of the anterior border of the trapezius, at the junction of its middle and inferior tbirds. The lesser occipital nerve curves round the accessory from below upwards, superficially, just at the posterior border of the muscle; it furnishes, therefore, a useful guide to the position of that important motor nerve.

The dorsalis scapulæ nerve (O.T. nerve to the rhomboids) crosses the triangle, inferior to the accessory, and enters the septum between the levator scapulæ and scalenus medius muscles.

The supra-scapular nerve is seen arising from the lateral edge of the upper trunk of the brachial plexus, a little above the posterior belly of the omo-hyoid muscle. The loops of the cervical plexus lie under cover of the upper part of the sterno-mastoid muscle, between it and the origins of the levator scapulæ and the upper part of the scalenus medius muscles.

The posterior belly of the omo-hyoid, which forms the superior boundary of the subclavian division of the posterior triangle, passes beneath the posterior border of the sterno-mastoid at a point about one inch above the clavicle. The external jugular vein, usually visible through the skin, runs in a line from the angle of the jaw to the middle of the clavicle ; it is the vessel which is generally opened to relieve the right side of the heart in asphyxia. The lumen of the vein is kept patent where it pierces the fascia of the subclavian triangle; hence a wound of the vein in that situation is liable to be followed by the suction of air into the circulation during inspiration. The third part of the subclavian artery can be compressed against the first rib by pressing downwards and backwards, immediately above the clavicle, a little behind the posterior border of the sterno-mastoid muscle. To map out the course of the subclavian artery in the neck, draw a line, convex upwanis, from the superior border of the sterno-clavicular articulation to the middle of the clavicle, the highest part of the arch to reach from ļ to 1 in. above the bone. To ligature the vessel in the third part of its course, an angular incision is made along

, of the superior border of the clavicle and the inferior part of the posterior he sterno-mastoid muscle. The most important guides to the vessel are ior belly of the omo-hyoid, the lateral border of the scalenus anterior, and e tubercle of the first rib. The close relation of the vessel to the lowest che brachial plexus and to the cervical pleura must be kept in mind. In nstances in which a cervical rib is present the subclavian artery lies either of it, or arches above it, according to the degree of development of the rib. avian vein lies below, and anterior to the artery, altogether under cover of ole. ring the posterior triangle, from behind the lateral border of the scalenus are the trunks of the brachial plexus. They lie upon the scalenus medius, be felt, through the skin, immediately above and behind the third part ubclavian artery. The anterior ramus of the fifth cervical nerve supplies omboids, the abductors and lateral rotators of the arm, and the flexors inators of the forearm; that of the sixth the serratus anterior, the adductors dial rotators of the arm, and the extensors and pronators of the forearm ; the seventh the flexors and extensors of the wrist; that of the eighth the and extensors of the fingers; that of the first thoracic all the small muscles hand. The carotid tubercle lies between the anterior rami of the sixth venth cervical nerves. The fifth and sixth cervical nerves are those which most when the plexus is injured by forcible depression of the shoulder the head is bent to the opposite side, such as occurs, for instance, in the etrical Paralyses” of Duchenne.

expose the trunks of the brachial plexus an incision is made from the on of the middle and inferior thirds of the posterior border of the sternoid downwards and laterally to the junction of the lateral and intermediate s of the clavicle. he relation of the lowest trunk of the brachial plexus to the first rib is rtant in relation to those forms of brachial neuritis in which the motor sensory symptoms indicate pressure on the anterior ramus of the first acic nerve.

Wood Jones has shown that the sulcus for the subclavian artery he superior surface of the first rib frequently lodges the lowest trunk of the hial plexus as well as the artery, and that the more the first thoracic nerve ributed to the plexus the deeper is the sulcus. In two cases the writer has d the neuralgia and the partial paralysis of the intrinsic muscles of the hand plied by the first thoracic nerve by removing the portion of the first rib coning the “sulcus nervi brachialis.” The symptoms were due to the portion of first thoracic nerve which goes to join the brachial plexus being stretched and ssed upon by the first rib as it crosses its inner edge to join the eighth cervical ve. Although similar symptoms may be produced by the first thoracic nerve ng stretched across a cervical rib, the surgeon must not expect to find this omaly in all cases; and when a skiagram has been obtained, care must be taken t to mistake a well-developed posterior tubercle of the transverse process of the venth cervical vertebra for a foreshortened view of a rudimentary cervical rib.

In the median line of the neck posteriorly is the nuchal furrow, at the bottom of hich are the cervical spines and the ligamentum nuchæ. At the superior part of ne furrow, about two inches below the external occipital protuberance, is the large pine of the epistropheus, which can be distinctly felt; a line drawn from it laterally nd slightly upwards to the transverse process of the atlas corresponds to the position f the inferior oblique muscle and, therefore, to the inferior margin of the sub-occipital riangle. The course of the deep part of the greater occipital nerve may be mapped out by drawing a line from the centre of the above-mentioned line to a point one inch lateral to the external occipital protuberance. In the floor of the suboccipital triangle is the posterior arch of the atlas upon which the vertebral artery lies.

THE THORAX. For the convenience of topographical description, clinicians, by the use of vertical and transverse lines, have arbitrarily divided the surface of the chest into

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Fig. 1090.- ANTERIOR ASPECT OF TRUNK, SHOWING SURFACE TOPOGRAPHY OF VISCERA. M.C. Mid-clavicular line.

T. Tricuspid orifice. A.C. Ascending colon. P.S. Para-sternal line.

R.L. Right lung.

T.C. Transverse colon. P. Inguinal vertical line.

L.L. Left lung.

D.C. Descending colon. I.C. Infracostal line.

Pl. Pleura.

IL.C. Hiac colon. T. Intertubercular line.

L. Liver.

P.C. Pelvic colon. Py. Transpyloric line of Addison. 0. Esophagus,

R. Rectum. A. Aorta.

St. Stomach,

C.I.

Common iliac artery. H. Heart.

Pylorus.

E.I. External iliac artery.
P.
Pulmonary orifice.

D. Duodenum.

I.V.C. Inferior vena cava
A.
Aortic orifice.

I. Ileum.

U. Umbilicus. M. Mitral orifice.

V. Valve of the colon.

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The adily suuntin i be a The inf

Py.

efinite regions or areas. The vertical lines are: the mid-sternal, the rnal, the para-sternal, the mammary or mid-clavicular, the anterior, mid, rior axillary, and the scapular. The position of the mid- and lateral nes is sufficiently indicated by their names. mammary, better termed the mid-clavicular, is drawn vertically downwards

centre of the clavicle, or, what comes to practically the same thing, from a dway between the centre of the jugular notch and the tip of the acromion. male this line usually lies 1 to fin. medial to the centre of the nipple, s usually placed over the fourth interspace, or fifth rib, four inches from ian plane. In the child the nipple may be as high as the inferior border of d rib. In the female the position of the nipple is so variable that it is of graphical value. In a well-proportioned subject, the mid-clavicular line, if ed downwards, will be found to be continuous with the vertical or lateral I line, which crosses the costal margin at the tip of the ninth costal cartilage. -para-sternal line, drawn midway between the lateral sternal and midlar, crosses the costal margin opposite the tip of the eighth costal cartilage. e anterior, the mid, and the posterior axillary lines are drawn downwards he anterior fold, the apex, and the posterior fold of the axilla, respectively. e scapular line is drawn perpendicularly through the inferior angle of the a.

the two transverse lines, the superior, which separates the infra-clavicular and sternal regions from the mammary and infra-sternal regions, is drawn at the of the third chondro-sternal articulation ; the inferior, which separates the nary and infra-mammary regions, is drawn at the level of the sixth chondroal articulation. he lateral area of the chest is divided into a superior, or axillary, and an inferior Era-axillary region, by a horizontal line drawn at the level of the sixth rib.

muscular subjects there is a well-marked median furrow, the sternal furrow, een the sternal origins of the pectoralis major muscles. The medial part of the ior border of each of these muscles forms a curved prominence which, overlying fifth rib, corresponds to the junction of the mammary and infra-mammary ons. Below this prominence is the infra-mammary region, which forms a ewhat flat surface, corresponding to the upper part of the rectus muscle. In axillary and infra-axillary regions are the prominences caused by the digitations origin of the serratus anterior, the first to appear below the pectoralis major ng that which springs from the fifth rib. The superior border of the sternum lies in the same horizontal plane as the erior border of the body of the second thoracic vertebra, the distance between the o being about two inches. The junction of the manubrium and the body of the ernum forms a slight prominence or angle, known as the angulus sterni

udovici), which, although not usually visible, may always be felt. The angulus es in the same plane as the body of the fifth thoracic vertebra.

The xiphi-sternal junction corresponds to the fibro-cartilage between the ninth nd tenth thoracic vertebræ. Immediately inferior to the xiphi-sternal articulation the infra-sternal notch, formed by the junction of the seventh costal cartilages rith the sternum. Inferior to the notch is the epigastric fossa or triangle, bounded aterally by the seventh costal cartilages. The apex of the triangle forms an angle which varies considerably according to the shape of the chest, the average being about 70°. Not infrequently the eighth costal cartilage articulates with the sternum.

Fracture of the sternum is rare, and generally occurs at or close to the junction of the manubrium and the body; it may occur either from direct violence, or indirectly along with fracture of the vertebral column. Unlike that of the ribs, the periosteum covering the sternum is firmly adherent to the bone.

The ribs, which in well-nourished subjects cause no surface prominences, are readily visible in thin persons; in the obese they are very difficult to feel. In counting the ribs from the front, the second may always be identified by its relation to the angulus sterni. The first rib is to a large extent under cover of the clavicle. The inferior border of the pectoralis major and the first visible digitation of the

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