198 APPLIED ANATOMY. 



almost in a straight line until opposite the fourth costal cartilage, where they begin to 

 diverge. The border of the right lung proceeds downward and begins to turn out- 

 ward opposite the sixth cartilage. 



The left lung on reaching the level of the fourth costal cartilage curves outward 

 and downward across the fourth interspace to a point about 2.5 cm. to the inner 

 side of the nipple in the fourth interspace. From this point it goes downward and 

 inward across the fifth rib and interspace to the top of the sixth rib about 3 cm. to 

 the inner side of the nipple line. This isolated tip of lung just above the sixth rib 

 over the apex beat of the heart is called the lingula. 



Lower Border. The lower edge of the lung varies in different individuals 

 and in the same individual according to the amount of inflation. In quiet respi- 

 ration it is about opposite the sixth cartilage and rib from the sternum to the mam- 

 mary line, opposite the eighth in the midaxillary line, the tenth in the scapular line, 

 and the eleventh near the vertebrae. 



The Fissures and Lobes of the Lungs. The left lung has one fissure and 

 two lobes, an upper and a lower. 



The right lung has two fissures and three lobes, an upper, a middle, and a lower. 



The fissure of the left lung begins above and posteriorly opposite the root of the 

 spine of the scapula; this is level with the fourth rib and third dorsal spine. It passes 

 downward and forward, ending at the sixth rib in the parasternal line. It crosses the 

 fourth in the midaxillary line. The lower lobe of the right lung is of the same size 

 as that of the left side. The lung above it is divided into a middle and upper lobe. 

 The main fissure of the right lung corresponds in its course almost exactly with that 

 of the left lung. It begins above and posteriorly at the root of the spine of the 

 scapula and passing downward crosses the fourth rib in the midaxillary line and ends at 

 the sixth rib in the mammary line (instead of the parasternal line as in the left). 



The subsidiary fissure of the right lung leaves the main fissure at the posterior 

 axillary line opposite the fourth rib and follows this rib in an almost horizontal direc- 

 tion to its junction with the sternum. 



In order to recognize and appreciate the changes which occur in the lungs in 

 lobar pneumonia it is necessary to know the outlines and limits of the various lobes of 

 the lungs. A knowledge of the exact course of the fissures of the lungs is not only 

 necessary to outline the lobes, but it is of service in the diagnosis of pleural effusions. 

 These effusions often are limited to certain localized areas instead of being general. 



Pleurisy may affect the lung bordering the fissures. When such is the case, the 

 effusion, serous or purulent, may be in the fissure itself and embrace but little of the gen- 

 eral pleural cavity. Dry taps from failure to hit the purulent or serous collection are 

 not infrequent, and the possibility of its being interlobular should be borne in mind. 



GENERAL CONSIDERATIONS. 



From what has been said it follows that a knowledge of the extent and outlines 

 of the lungs and of the location and course of the fissures is essential to the proper 

 diagnosis and treatment of affections of both the lungs and pleurae. 



The extent of the lungs is determined in the living by percussion. The apex of 

 the lungs forms an oblique plane running upward and backward from just below the 

 lower edge of the inner extremity of the clavicle to the neck of the first rib above 

 and posteriorly. The level of these two points will vary according to the inclination 

 of the ribs, which in turn is influenced by the direction (vertical) of the spine. Ordi- 

 narily the distance is 5 cm. (2 in.). It may be even as much as 7 or 8 cm. The 

 top edge of the clavicle passes across the middle of this distance so that the top of 

 the lung is about 2. 5 cm. ( i in. ) above the clavicle. The highest point of the lung 

 is not in the middle of the space enclosed by the first rib, but is at its posterior 

 border, at the neck of the first rib. 



In percussing, one should not strike directly backward but both downward and 

 backward. 



If the patient is standing erect the first rib will slope downward and forward at an 

 angle of 65 degrees, or more, with a vertical line. The spine will slope downward and 

 backward from the same vertical line in a normally straight back about 20 degrees. 



