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The roots of the lungs are situated opposite the fourth, fifth, and sixth thoracic spines, midway between them and the vertebral margins of the scapula.

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Crus of diaphragm

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FIG. 1095. DISSECTION FROM BEHIND TO SHOW THE RELATION OF THE TWO PLEURAL SACS TO THE KIDNEYS. Outlines of superior portions of the two kidneys are indicated by dotted lines. (From Cunningham.)

The lower end of the trachea, the bronchi, the vagi, and the left recurrent nerve, are all more or less surrounded by lymph glands, which, when enlarged, may exert injurious pressure upon them.

THE HEART AND GREAT VESSELS.

Viewed from the front, the outline of the precordial area, like that of the pericardial sac, is roughly triangular, the base of the triangle being below and the apex above. The boundaries are delineated upon the surface as follows:

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The right side of the triangle, formed by the right atrium, is indicated by drawing a line slightly convex laterally from the superior end of the third to the sixth costal cartilage, a finger's breadth from the edge of the sternum; the curve attains its maximum opposite the fourth intercostal space, where it reaches one and a half inch from the median plane.

The base of the triangle, formed by the margo acutus of the right ventricle and to a very slight extent by the apical portion of the left ventricle, is almost horizontal, and corresponds to a line drawn from the inferior extremity of the right side of the triangle to the apex of the left ventricle, which lies behind the fifth left intercostal space, three and a half inches from the median plane, and half an inch medial to the mid-clavicular line. The base line crosses the xiphoid process at its junction with the body of the sternum.

The left side of the triangle, formed by the margo obtusus of the left ventricle, is indicated by a slightly curved line extending from the apex of the heart upwards to the inferior edge of the second interspace, a finger's breadth from the sternum, the convexity of the curve being directed laterally and slightly upwards.

The truncated apex of the triangle, which lies behind the sternum at the level of the second intercostal space, corresponds to the highest part of the heart, namely, where the auricles of the atria embrace the aorta and pulmonary artery.

The situation of the anterior part of the coronary sulcus is mapped out by a line drawn from the median plane, opposite the inferior border of the third left costal cartilage, downwards and laterally to the sixth right chondro- sternal junction; the line should be slightly convex upwards and to the right. The right auricle lies at, or a little to the right of, the median plane, at the level of the second

T.

Trachea.
Aorta.

A.

L. L. Left lung. R. L. Right lung. St. Stomach.

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Sp. Spleen. L. Liver.

S.R. Suprarenal gland.
L.K. Left kidney.
R.K. Right kidney.

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FIG. 1096.-POSTERIOR ASPECT OF TRUNK, SHOWING SURFACE TOPOGRAPHY OF VISCERA.

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Pancreas.

Pleura.

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P. Pl.

D.C. Descending colon. A.C. Ascending colon. R. Rectum.

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The diaphragmatic or inferior surface of the heart rests upon the diaphragmatic or basal part of the pericardium. The base, or true posterior surface, of the heart is formed mainly by the left atrium, which is moulded posteriorly upon the oesophagus, the aorta, the bronchi, and the bronchial glands, the pericardium intervening. The left atrium extends behind the right atrium for a considerable distance to the right of the median plane.

In a radiographic examination in cases of general visceroptosis, the diaphragm, which should rise and fall opposite the xiphisternal junction, will be seen to be an inch or more lower down, while the heart is seen to hang more vertically than normal (cardioptosis).

In determining the position of the cardiac orifices and their valves it is to be remembered that they are all situated below and to the left of the anterior part of the coronary sulcus, and that they lie in the following order from above downwards—viz., pulmonary, aortic, mitral, and tricuspid. When delineated on the surface they will be seen to lie within an ellipse whose long axis extends from the superior border of the third left to the sixth right chondro-sternal junction.

The pulmonary orifice, directed upwards and slightly backwards and to the left, lies opposite the superior border of the third left chondro-sternal junction; the aortic orifice, directed upwards, backwards, and to the right, lies further from the surface, behind the left half of the sternum, opposite the inferior border of the third costal cartilage; the mitral orifice lies at an inferior level, behind the left half of the sternum, opposite the fourth rib; the orifice of the opening is directed downwards, forwards, and to the left. The tricuspid orifice, situated nearer the anterior wall of the chest than the mitral, lies very obliquely behind the right half of the sternum at the level of the fourth and fifth cartilages and intervening space.

Although the first and second sounds of the heart are heard all over the cardiac area, the sounds produced by the individual valves are heard most distinctly, not directly over their anatomical situation, but over the area where the cavity in which the valve lies approaches nearest to the surface. Hence the mitral sound is best heard over the apex (mitral area), the tricuspid over the inferior part of the body of the sternum (tricuspid area), the aortic over the second right costal cartilage (aortic area), and the pulmonary over the second left intercostal space (pulmonary area).

In tapping the pericardium (paracentesis pericardii) the pleura will be avoided by making the puncture through the fifth or sixth left intercostal space as close as possible to the edge of the sternum. When, however, the pericardial sac is distended with fluid, the pleura is pushed laterally, and will therefore escape injury if the puncture is made at a safe distance lateral to the internal mammary vessels, viz., one inch lateral to the left border of the sternum.

To establish free drainage in suppurative pericarditis, the sixth left costal cartilage must be resected and the internal mammary vessels ligatured; the transversus thoracis and the pleural reflection are then pushed aside and the pericardium exposed and incised.

The ascending aorta lies behind the sternum, opposite the second and third ribs, and, unless dilated, does not project beyond its right border. The superior border of the aortic arch lies at or a little above the centre of the manubrium sterni; in the child the vessel may reach as high as the superior border of the manubrium.

The innominate and left common carotid arteries diverge from either side of the median plane between the upper part of the manubrium sterni and the front of the trachea. A pin pushed directly backwards immediately above the middle of the supra-sternal notch will strike the medial border of the innominate artery a little below its bifurcation.

The pulmonary artery lies behind the left border of the sternum opposite the second interspace and the second costal cartilage.

The left innominate vein lies behind the superior part of the manubrium sterni, the right behind the medial end of the right clavicle. The superior vena cava lies immediately to the right of the margin of the sternum, opposite the first and second interspaces and the intervening second rib; its opening into the right atrium, behind the third chondro-sternal articulation, corresponds to the centre of the root of the right lung.

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R. A. R.V.

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Right atrium. Right ventricle. Left atrium. L.A.A. Left auricle. S.V.

Interventricular septum.

P.A. Pulmonary artery.
P.V. Pulmonary valve.
A. Aortic arch.
A.V. Aortic valve.
T.V. Tricuspid valve.

R.V.

FIG. 1100.

FIG. 1099.
From photographs of a formalin-hardened subject, with the heart dissected in situ, to show the relations of its
cavities and valves to the anterior wall of the thorax.

In Fig. 1097 the anterior wall of the right ventricle has been removed and the pulmonary artery opened.
In Fig. 1098 the anterior walls of the ascending aorta and of the right atrium have been removed; also the
anterior cusp of the tricuspid valve.

In Fig. 1099 the greater part of the interventricular septum has been removed, exposing the anterior cusp of
mitral valve.

In Fig. 1100 the ascending aorta, anterior cusp of mitral valve, trunk of pulmonary artery, and interauricular septum have been removed; the cavities of the left atrium and left ventricle are exposed, also the left auricle and posterior cusp of mitral valve.

M.V. Mitral valve.

S.V.C. Superior vena cava.
P.V.
M.

Pulmonary vein.

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CESOPHAGUS.

The average length of the œsophagus in the adult is 10 in. (25 cm.); the listance from the incisor teeth to its commencement is 6 in.; to the point or evel where it is crossed by the left bronchus, 9 in.; to the oesophageal opening of the diaphragm, 14 to 15 in.; to the cardiac orifice of the stomach, 16 in. These measurements, which are of great importance in diagnosing the seat of oesophageal obstructions, should be marked off from below upwards upon all œsophageal Dougies and probangs. Posteriorly, the oesophagus extends from the level of the sixth cervical spine to that of the tenth thoracic, a little to the left of which is the situation at which the stethoscope is placed in order to hear the sound produced by the passage of fluid into the stomach.

Clinically it is important to bear in mind the relation of the oesophagus to the trachea and left bronchus, to the left recurrent nerve, to the bronchial and posterior mediastinal glands, to the descending thoracic aorta, and to the right posterior mediastinal pleura. Ulcers of the œsophagus are liable to open into either the trachea, the left bronchus, or the right pleura.

The veins of the inferior end of the oesophagus open partly into the systemic veins and partly into the portal system; like those at the inferior end of the rectum they are liable to become varicose in conditions which give rise to chronic interference with the portal circulation.

The lymph vessels of the upper part of the oesophagus open into the inferior deep cervical glands, the remainder into the posterior mediastinal glands.

The oesophagus is very distensible in the transverse but not in the antero-posterior direction, hence the most useful forceps for removing foreign bodies from the œsophagus are those which open laterally.

THE ABDOMEN.

THE ANTERIOR ABDOMINAL WALL.

The configuration of the abdomen varies with the age, sex, obesity, and muscular development of the individual. In the child it is wider above than below, while the reverse is the case in the adult female. It is most prominent in the region of the umbilicus, which is situated, normally, below the mid-point between the infrasternal notch and the symphysis pubis, usually a little below the level of the highest part of the iliac crest, and opposite the middle of the body of the fourth lumbar vertebra. In the obese, and especially when the abdominal muscles have lost their tone, the umbilical region becomes prominent and more or less pendulous, so that the umbilicus may come to lie considerably below the normal level. In the child it is relatively lower than in the adult, in consequence of the undeveloped state of the pelvis.

In spare subjects the inferior end of the body of the sternum, the xiphoid process, and the costal margin, can readily be traced. The slight depression or notch formed by the seventh costal cartilages and the inferior border of the body of the sternum is termed the infrasternal notch. Below the notch, and bounded on each side by the seventh, eighth, and ninth costal cartilages, is the infracostal angle, which varies considerably according to the shape of the chest; it is relatively wider in the child than in the adult. The inferior border of the curve of the tenth costal cartilage is easily recognisable, and was selected by Cunningham as the level of the plane of separation (infracostal plane) between the upper and middle abdominal zones.

The anterior abdominal wall is limited below by the fold of the groin and the crest of the pubes. In a spare muscular subject the recti, the furrows corresponding to the inscriptiones tendineæ (O.T. lineæ transversa) and the supra-umbilical portion of the linea alba, can be readily made out. When the outline of the rectus is not visible the lateral border may be indicated by a line drawn from the tip of the ninth costal cartilage to the mid-point of a line joining the umbilicus and the anterior superior iliac spine, and from thence to the pubic tubercle. In the angle between the lateral border of the rectus and the ninth costal cartilage, on the right side, is a slight triangular depression which overlies the fundus of the gall-bladder. Between the inferior part of the lateral border of the rectus and the prominence above the anterior part of the iliac crest, caused by the lower

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