THE LUNGS. 977 



accompanying the bronchial tubes, are distributed to the bronchial glands, and 

 upon the walls of the larger bronchial tubes and pulmonary vessels. Those sup- 

 plying the bronchial tubes form a capillary plexus in the muscular coat, from 

 which branches are given off to form a second plexus in the mucous coat. This 

 plexus communicates with branches of the pulmonary artery, and empties itself 

 into the pulmonary vein. Others are distributed in the interlobular areolar tissue, 

 and terminate partly in the deep, partly in the superficial, bronchial veins. Lastly, 

 some ramify upon the surface of the lung beneath the pleura, where they form a 

 capillary network. 



The bronchial vein is formed at the root of the lung, receiving superficial and 

 deep veins corresponding to branches of the bronchial artery. It does not, how- 

 ever, receive all the blood supplied by the artery, as some of it passes into the 

 pulmonary vein. It terminates on the right side in the vena azygos major, and 

 on the left side in the superior intercostal or left upper azygos vein. 



The lymphatics consist of a superficial and deep set : they terminate at the 

 root of the lung, in the bronchial glands. 



Nerves. The lungs are supplied from the anterior and posterior pulmonary 

 plexuses, formed chiefly by branches from the sympathetic and pneumogastric. 

 The filaments from these plexuses accompany the bronchial tubes, upon which 

 they are lost. Small ganglia are found upon these nerves. 



Surface Form. The apex of the lung is situated in the neck, behind the interval between 

 the two heads of origin of the Sterno-mastoid. The height to which it rises above the clavicle 

 varies very considerably, but is generally about one inch. It may, however, extend as much as 

 an inch and a half or an inch and three-quarters, or, on the other hand, it may scarcely project 

 above the level of this bone. In order to mark out the anterior margin of the lung, a line is 

 to be drawn from the apex-point, one inch above the level of the clavicle, and rather nearer the 

 posterior than the anterior border of the Sterno-mastoid muscle, downward and inward across 

 the sterno-clavicular articulation and first piece of the sternum until it meets, or almost meets, 

 its fellow of the other side opposite the articulation of the manubrium and gladiolus. From this 

 point the two lines are to be drawn downward, one on either side of the mesial line and close to 

 it, as far as the level of the articulation of the fourth costal cartilages to the sternum. From 

 here the two lines diverge ; the left is to be drawn at first passing outward with a slight inclina- 

 tion downward, and then taking a bend downward with a slight inclination outward to the apex 

 of the heart, and thence to the sixth costo-chondral articulation. The direction of the anterior 

 border of this part of the left lung is denoted with sufficient accuracy by a curved line with its 

 convexity directed upward and outward from the articulation of the fourth right costal cartilage 

 of the sternum to the fifth intercostal space, an inch and a half below and three-quarters of an 

 inch internal to the left nipple. The continuation of the anterior border of the right lung is 

 marked by a prolongation of its line from the level of the fourth costal cartilages vertically 

 downward as far as the sixth, when it slopes off' along the line of the sixth costal cartilage to its 

 articulation with the rib. 



The lower border of the lung is marked out by a slightly curved line with its convexity down- 

 ward from the articulation of the sixth costal cartilage to its rib to the spinous process of the 

 tenth dorsal vertebra. If vertical lines are drawn downward from the nipple, the mid-axillary 

 line, and the apex of the scapula, while the arms are raised from the sides, they should intersect 

 this convex line, the first at the sixth, the second at the eighth, and the third at the tenth rib. 

 It will thus be seen that the pleura (see page 971) extends farther down than the lung, so that 

 it may be wounded, and a wound pass through its cavity into the Diaphragm, and even injure 

 the abdominal viscera, without the lung being involved. 



The posterior border of the lung is indicated by a line drawn from the level of the spinous 

 process of the seventh cervical vertebra, down either side of the spine, corresponding to the 

 costo-vertebral joints as low as the spinous process of the tenth dorsal vertebra. The trachea 

 bifurcates opposite the spinous process of the fourth dorsal vertebra, and from this point the two 

 bronchi are directed outward. 



The position of the great fissure in the right lung may be indicated by a line drawn from 

 the fourth dorsal vertebra round the side of the chest to the anterior margin of the lung opposite 

 the seventh rib, and the smaller or secondary fissure by a line drawn from the preceding where 

 it bisects the mid-axillary line to the junction of the fourth costal cartilage to the sternum. The 

 great fissure in the left lung is a little higher, extending from the third dorsal vertebra round the 

 side of the chest to reach the anterior margin of the lung opposite the sixth costal cartilage. 



Surgical Anatomy. The lungs may be wounded or torn in three ways : (1) By compres- 

 sion of the chest, without any injury to the ribs. (2) By a fractured rib penetrating the lung. 

 ( 3) By stabs, gunshot wounds, etc. 



The first form, where the lung is ruptured by external compression without any fracture 

 of the ribs, is very rare, and usually occurs in young children, and affects the root of the lung 

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