350 THE RESPIRATORY SYSTEM 



Surface Marking of Lung Fissures. The oblique fissure of 

 the lung corresponds to a line drawn from the second thoracic 

 spine downwards and laterally through the root of the spine of 

 the scapula and across the infra-spinous fossa. It is continued 

 downwards and forwards round the side of the body, and cuts 

 the inferior border of the lung on the sixth costal cartilage. 

 The transverse fissure may be indicated by a line drawn hori- 

 zontally to the right from the middle of the sternum at the 

 level of the fourth costal cartilage until it meets the oblique 

 fissure in the mid-axillary line. 



When the fissures are mapped in on the surface, it is found 

 that the upper lobe is most accessible from the anterior aspect 

 of the body, and the lower lobe from the lateral and posterior 

 aspects. The middle lobe of the right lung can only be satis- 

 factorily examined from the front of the chest, as it tails off 

 rapidly into the axilla. 



The relations of the fissures of the lung to the surface of 

 the chest are of importance in the diagnosis of interlobar 

 empyema. In this condition the area of dulness occurs on 

 the line of one of the fissures. 



The Apex of the Lung projects upwards into the root of the 

 neck for from a half to one inch above the clavicle, but this 

 upward projection is entirely due to the obliquity of the first 

 rib, which slopes downwards from the vertebral column to the 

 manubrium sterni. Anteriorly^ above the clavicle, the apex is 

 related to the sterno-mastoid and the scalenus anterior muscles, 

 and it is crossed by the first part of the subclavian artery. 

 Medially, it is related to the trachea, from which it is separated 

 by the carotid sheath and its contents. This relationship is of 

 importance because, owing to the slope of the neck, the apex 

 of the lung is usually percussed in a backward and medial 

 direction, and so the lung note is altered by the tracheal 

 resonance. To avoid this complication, direct backward per- 

 cussion may be employed or the tracheal resonance may be 

 more easily eliminated if the patient is instructed to keep the 

 mouth open during the examination. 



