THE ORGANS OF VOICE AND RESPIRATION 



from the outer to the inner surface of the lung both above and below the hilum. 

 As seen on the surface, this fissure commences on the inner aspect of the lung 

 at the upper and posterior part of the hilum, and runs backward and upward 

 to the posterior border, which it crosses about two and a half inches below the 

 apex. It then extends downward and forward over the outer surface and reaches 

 the lower border a little behind its anterior inferior extremity, and its further 

 course can be followed upward and backward across the inner surface as far as 

 the lower part of the hilum. The upper lobe (lobus superior} lies above and in 

 front of this fissure, and includes the apex, the anterior border, and a considerable 

 part of the outer surface and the greater part of the inner surface of the lung. The 



Lower edge 



of lung. \T\ 



Line of pleural 

 reflection on to 

 diaphragm. 



FIG. 909. Front view of chest, showing relations of pleurae and lungs to the chest wall. The blue lines 

 indicate the lines of the reflection of the pleurae; the red, the outlines of the lungs and their fissures. 



lower lobe (lobus inferior), the larger of the two, is situated below and behind 

 this fissure, and comprises almost the whole of the base, a large portion of the 

 outer surface, and the greater part of the posterior border. 



The right lung is divided into threejobes, upper, middle, and lower, by an oblique 

 and a horizontal fissure. The oblique fissure separates the lower from the middle 

 and upper lobes, and corresponds closely with the fissure of the left lung. Its 

 direction is, however, more vertical, and it cuts the lower border about three inches 

 behind its anterior inferior extremity. The horizontal fissure separates the upper 

 from the middle lobe. It begins in the oblique fissure near the posterior border 

 of the lung and, running horizontally forward, cuts the anterior border at the level 

 of the sternal end of the fourth costal cartilage; on the inner surface it may be traced 



