

SURFACE ANATOMY OF THE THORAX 1307 



Spinal Nerves (Fig. 1214). The table on page 1305, after Macalister, shows the 

 relations which the places of attachment of the nerves to the medulla spinalis 

 present to the bodies and spinous processes of the vertebrae. 





SURFACE ANATOMY OF THE THORAX. 





Bones. The skeleton of the thorax is to a very considerable extent covered by 

 muscles, so that in the strongly developed muscular subject it is for the most part 

 concealed. In the emaciated subject, however, the ribs, especially in the lower and 

 lateral regions, stand out as prominent ridges with the sunken intercostal spaces 

 between them. 



In the middle line, in front, the superficial surface of the sternum can be felt 

 throughout its entire length at the bottom of a furrow, the sternal furrow, situated 

 between the Pectorales majores. These muscles overlap the anterior surface 

 somewhat, so that the whole width of the sternum is not subcutaneous, and this 

 overlapping is greatest opposite the middle of the bone; the furrow, therefore, is 

 wide at its upper and lower parts but narrow r in the middle. At the upper border 

 of the manubrium sterni is the jugular notch: the lateral parts of this notch are 

 obscured by the tendinous origins of the Sternocleidomastoidei, which appear as 

 oblique cords narrowing and deepening the notch. Lower down on the subcu- 

 taneous surface is a well-defined transverse ridge, the sternal angle; it denotes the 

 junction of the manubrium and body. From the middle of the sternum the sternal 

 furrow spreads out and ends at the junction of the body with the xiphoid process. 

 Immediately below this is the infrasternal notch; between the sternal ends of the 

 seventh costal cartilages, and below the notch, is a triangular depression, the 

 epigastric fossa, in which the xiphoid process can be felt. 



On either side of the sternum the costal cartilages and ribs on the front of the 

 thorax are partly obscured by the Pectoralis major, through which, however, they 

 can be felt as ridges with yielding intervals between them corresponding to the 

 intercostal spaces. Of these spaces, that between the second and third ribs is the 

 widest, the next two are somewhat narrower, and the remainder, with the exception 

 of the last two, are comparatively narrow. 



Below the lower border of the Pectoralis major on the front of the chest, the 

 broad flat outlines of the ribs as they descend, and the more rounded outlines of the 

 costal cartilages, are often visible. The lower boundary of the front of the thorax, 

 which is most plainly seen by bending the body backward, is formed by the xiphjid 

 process, the cartilages of the seventh, eighth, ninth, and tenth ribs, and the ends of 

 the cartilages of the eleventh and twelfth ribs. 



On either side of the thorax, from the axilla downward, the flattened external 

 surfaces of the ribs may be defined. Although covered by muscles, all the ribs, 

 with the exception of the first, can generally be followed without difficulty over the 

 front and sides of the thorax. The first rib being almost completely covered by 

 the clavicle can only be distinguished in a small portion of its extent. 



At the back, the angles of the ribs lie on a slightly marked oblique line on either 

 side of, and some distance from, the spinous processes of the vertebrae. The line 

 diverges somewhat as it descends, and lateral to it is a broad convex surface caused 

 by the projection of the ribs beyond their angles. Over this surface, except where 

 covered by the scapula, the individual ribs can be distinguished. 



Muscles. The surface muscles covering the thorax belong to the musculature 

 of the upper extremity (Figs. 1215, 1219), and will be described in that section 

 (page 1325). There is, however, an area of practical importance bounded by these 

 muscles. It is limited above by the lower border of Trapezius, below by the upper 

 border of Latissimus dorsi, and laterally by the vertebral border of the scapula; the 





