9 2 



TOPOGRAPHIC AND APPLIED ANATOMY. 



fourth rib or of the fourth intercostal space. The posterior median furrow extends downward 

 from the vertebra prominens. It is produced chiefly by the prominences of the long muscles 

 of the back. In this furrow may be felt (or seen in emaciated subjects) the spinous pro- 

 cesses of the dorsal vertebras. The clavicles may be easily outlined, as may also their thickened 

 sternal ends and the sternoclavicular articulations. The injraclamcular fossa (Mohrenheim's 

 fossa) is situated below the junction of the middle and outer thirds of the clavicle and corresponds 

 to the groove between the pectoralis major and deltoid muscles ; it is more distinct in individuals 

 in whom there is a marked deviation between the borders of these muscles. In the bottom of 

 this fossa the costocoracoid ligament may sometimes be felt, running approximately parallel with 

 the clavicle. To the outer side of this ligament is the coracoid process, covered by the edge of the 



deltoid muscle. Passing the finger outward along the clavicle 

 we reach the acromion, and posteriorly we may palpate the 

 spine and the internal and inferior angles of the scapula. Below 

 the spine of the scapula may be felt the eighth, ninth, tenth, 

 and eleventh ribs. The edge of the pectoralis major leaves the 

 anterior thoracic wall and forms the anterior axillary fold; 

 posteriorly the edge of the latissimus dorsi muscle runs upward 

 and forms the posterior axillary fold. Below the axilla may 

 be more or less distinctly seen the serrations of the serratus 

 magnus muscle which interdigitate with those of the external 

 oblique and latissimus dorsi muscles. If the trapezius muscle 

 is put upon the stretch by drawing down the shoulder, its edge 

 may sometimes be seen, in lean subjects, passing to the 

 spinous process of the twelfth dorsal vertebra. 



The Bony Thorax. The bony thorax is the firm frame- 

 work of the chest and is shaped like a truncated cone with 

 the base downward and having a longer frontal and a shorter 

 sagittal diameter. The superior aperture of the thorax is 

 inclined anteriorly; its boundaries are formed by the upper 

 margin of the sternum, by the first pair of ribs, and by the 

 upper margin of the first dorsal vertebra. The relative short- 

 ness of the sagittal diameter of this opening should be well 

 borne in mind. The inferior aperture of the thorax is much 

 larger; its boundaries are formed by the xiphoid process of the 

 sternum, by the costal margin, by the free ends of the eleventh and twelfth ribs, and by the body 

 of the twelfth dorsal vertebra. The inferior aperture, unlike the superior one, lies in two planes 

 which form an angle, the apex being downward, at the lowest portion of the costal margin. 



The bony thorax is not firm enough to resist temporary or permanent changes of shape, 

 which may be produced as the result of pressure from without or from within. The deleterious 

 effects of pressure from without are particularly in evidence as a result of tight lacing (Fig. 40), 

 against which it is the duty of the mother and of the physician to exert a sturdy and continuous 

 opposition. Since the lower portion of the bony thorax surrounds some of the abdominal organs, 



FIG. 40.- 



-A thorax deformed by lacing 

 (after Merkel). 



