

 THE LUNGS 1199 



posterior than the anterior border of the Sternomastoid muscle, downward and inward across 

 the sternoclavicular 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 mesal 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 costochondral 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 in the male. 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 thoracic vertebra. If vertical lines are drawn downward from the middle of the clavicle, 

 from the deepest part of the axilla, and from 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 extends farther down 

 than the lung, so that it may be wounded, and a wound may pass through its cavity into the Dia- 

 phragm, and the abdominal viscera may be injured 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 vertebral column, correspond- 

 ing to the costovertebral joints as low as the spinous process of the tenth thoracic vertebra. 

 The trachea bifurcates opposite the spinous process of the fourth thoracic vertebra, and from this 

 point the two bronchi are directed outward. 



"The position of the great fissure of the lungs may be indicated by a line drawn from the third 

 thoracic spine obliquely downward in such a manner as to reach the sixth rib close to the mid- 

 clavicular line. The interlobar fissure between the upper and middle lobes of the right lung 

 corresponds to a line drawn from the apex of the axilla almost horizontally to the sternum, 

 reaching the latter at about the level of the fourth costal cartilage" (Ehrendrath). 



Applied Anatomy. The lungs may be wounded or torn in three ways: (1) By compression 

 of the thorax, 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 

 i. e., the most fixed part -and thus, implicating the great vessels, is frequently fatal. It would 

 seem to be a most unusual injury, and the exact mode of its causation is difficult to understand. 

 The probable explanation is that immediately before the compression is applied a deep inspira- 

 tion is taken and the lungs are fully inflated; owing then to spasm of the glottis at the moment 

 of compression, the air is unable to escape from the lung, the lung is not able to recede, and 

 consequently gives way. 



In the second variety, when the wound in the lung is produced by the penetration of a broken 

 rib, both the pleura costalis and the pleura pulmonalis must necessarily be injured, and conse- 

 quently the air taken into the wounded air cells may find its way through these wounds into the 

 cellular tissue of the parietes of the thorax. This it may do without collecting in the pleural 

 cavity; the two layers of the pleura are so intimately in contact that the air may pass straight 

 through from the wounded lung into the subcutaneous tissue. Emphysema constitutes, there- 

 fore, an important sign of injury to the lung in cases of fracture of the ribs. Pneumothorax, or air 

 in the pleural cavity, is much more likely to occur in injuries to the lung of the third variety; that 

 is to say, from external wound*, from stabs and gunshot injuries, in which cases air passes either 

 from the wound of the lung or from an external wound into the cavitv of the pleura during the 

 respiratory movements. In these cases there is generally no emphysema of the subcutaneous 

 tissue unless the external wound is small and valvular, so that the air drawn into the wound 

 during inspiration is then forced into the cellular tissue during expiration because it cannot 

 escape from the external wound. Occasionally in wounds of the parietes of the thorax no 

 air finds its way into the cavity of the pleura, because the lung at the time of the accident 

 protrudes through the wound and blocks the opening. This occurs where the wound is large, 

 and constitutes a so-called hernia of the lung. True hernia of the lung occurs, though very 

 rarely, after wounds of the thoracic wall, when the wound has healed and the cicatrix subse- 

 quently yields from the pressure of the viscus behind. It forms a globular, elastic, crepitating 

 swelling, which enlarges during expiratory efforts, falls during inspiration, and disappears on 

 holding the breath. Wounds of the lung may produce dangerous or fatal hemorrhage into the 

 pleural sac. In many cases the bleeding is spontaneously arrested; in others the surgeon must 

 interfere to save life. In some cases air has been admitted by intercostal incision and the inser- 



