532 



HUMAN ANATOMY. 



above the symphysis it widens into a narrow triangle (adminiculum), but is still 

 not visible on account of the suprapubic fat. It may be congenitally mush wider 

 than normal, or may be stretched by abdominal swellings, and in either case may 

 be the seat of ventral hernia. The absence of blood-vessels in and over the linea 

 alba and its thinness lead to its selection as the site of the incision in many 

 abdominal operations. 



The linea semilunaris, corresponding to the other border of the sheath of the 

 rectus muscle, may be seen when the rectus contracts as a curved line from 6.5 to 

 7.5 cm. (25^-3 in.) external to the linea alba, at the level of the umbilicus, with its 



Fig. 533. 



'W^ ' 



Infraclavicular fossa 



Coracoid process 



Groove between deltoid- 

 and pectoralis major 



/ 



, Sujirasternal notch 



Clavicle 

 /^ ^Sternum 



'Acromion 



Deltoid 



X-rib cartilage 



Linea 

 semilunaris 



p:iisiform cartilage 



liifrasternal 

 depression 



Linea alba 



Linea 

 transversa 



Anterior superior iliac spine 



Line of Poupart's ligament 



^^perniatic cord emerging 

 at external abdominal 

 ring 



Anterior surface of trunk, from photograph of living model ; bony landmarks have been somewhat exaggerated. 



concavity inward, extending from the tip of the ninth costal cartilage to the spine of 

 the pubes. As it marks the point of division of the abdominal aponeuroses 

 (Fig. 529) to form the sheath of the rectus, it also marks a frequent line of limita- 

 tion of emphysematous, hemorrhagic, or purulent extravasations in the lateral inter- 

 muscular spaces i^vide siipi-a). 



The linecB trarisversce, which may also be seen as shallow grooves when the 

 rectus is in action, and are most marked in muscular persons, correspond to the 

 tendinous intersections that interrupt the longitudinal fibres of the rectus. They 

 are the representatives of the intersegmental septa which separate the original 



