PRACTICAL CONSIDERATIONS : THE THORAX. 171 



centimetres (one inch) external to the costo-chondral junction, or about ten centi- 

 metres (four inches) from the middle line. Its position is variable, and is much 

 lower in fat persons, especially females. In emphysema the nipple may remain 

 stationary, while the upper ribs ascend, and it may be opposite the fifth, sixth, 

 seventh, or even the eighth rib. In phthisis with a shallow depressed chest it may 

 be opposite the fourth rib. A line drawn horizontally from the nipple around the 

 chest is on a level with the sixth intercostal space at the mid-axillary line. 



A horizontal line around the trunk on the level of the angle of the scapula (the 

 arms hanging down) would traverse the sternum between the fourth and fifth ribs, 

 the fifth rib at the nipple line, and the ninth rib at the vertebral column (Treves). 



The sternum is subcutaneous in the groove between the pectoral muscles. 

 Near the upper third the ridge between the manubrium and body may be seen or 

 felt. It is on a level with the second costal cartilage. This cartilage projects for- 

 ward more than the others. As the origins of the pectoral muscles diverge the 

 sternal groove becomes broader. It ends at the lower portion of the body of the 

 sternum in a slight projection usually seen and easily felt. This marks the upper 

 limit of the " infrasternal depression" (^epigastric fossa, scrobiculus cordis^, the 

 floor of which is over the ensiform process, and which is bounded laterally by the 

 seventh costal cartilages and inferiorly by the upper ends of the recti muscles. In 

 many abdominal diseases, and sometimes after laparotomies, the obliteration of this 

 depression (by the occurrence of tympany) is an important clinical symptom. 



When the arm is raised, the highest visible digitation of the serratus corre- 

 sponds to the fifth rib ; the largest is that attached to the sixth rib. 



During expiration the upper end of the sternum is on a level with the second 

 dorsal intervertebral disk ; the line between the manubrium and body is oh a level 

 with the fifth thoracic vertebra ; the junction of the sternal body and the ensiform 

 process is opposite the lower part of the ninth thoracic vertebra. 



The eleventh and twelfth ribs can be felt as blunt bony projections directed 

 downward and outward just outside the erector spinae muscles. 



(The relations of the various thoracic viscera to the chest-wall will be con- 

 sidered in connection with the anatomy of the former. ) 



