VASTUS EXTERNUS AND INTERNUS. 257 



longus, an isosceles triangle, whereof the base corresponds with Pou- 

 part's ligament. A perpendicular line, drawn from the middle of the 

 base to the apex of this triangle, immediately overlies the femoral 

 artery with its sheath. 



The RECTUS (straight) muscle is fusiform in its shape and bipenni- 

 form in the disposition of its fibres. It arises by two round tendons, 

 one from the anterior inferior spinous process of the ilium, the other 

 from the upper lip of the acetabulum ; and is inserted by a broad and 

 strong tendon, into the upper border of the patella. It is more correct 

 to consider the patella as a sesamoid bone, developed within the 

 tendon of the rectus ; and the ligamentum patellae as the continuation 

 of the tendon to its insertion into the tubercle of the tibia. 



Relations. By its superficial surface with the gluteus medius, psoas 

 and iliacus, sartorius ; and, for the lower three -fourths of its extent, 

 with the fascia lata. By its deep surface with the capsule of the hip- 

 joint, the external circumflex vessels, crureus, and vastus internus 

 and externus. 



The rectus must now be divided through its" middle, and the two 

 ends turned aside, to bring clearly into view the next muscles. 



The three next muscles are generally considered collectively under 

 the name of triceps extensor cruris. Adopting this view, the muscle 

 surrounds the whole of the femur, excepting the rough line (linea 

 aspera) upon its posterior aspect. Its division into three parts is not 

 well defined ; the fleshy mass upon each side being distinguished by 

 the names of vastus internus and externus, the middle portion by that 

 of crureus. 



The VASTUS EXTERNUS, narrow below and broad above, arises 

 from the outer border of the patella, and is inserted into the femur 

 and outer side of the linea aspera, as high as the base of the trochanter 

 major. 



Relations. By its superficial surface with the fascia lata, rectus, 

 biceps, semi-membranosus and gluteus maximus, a synovial bursa 

 being interposed between it and the latter. By its deep surface with 

 the crureus and femur. 



The VASJWJS INTERNUS, broad below and narrow above, arises 

 from the inner border of the patella, and is inserted into the femur 

 and inner side of the linea aspera as high up as the anterior intertro- 

 chanteric line. 



Relations. By its superficial surface with the psoas and iliacus, 

 rectus, sartorius, femoral artery and vein and saphenous nerves, pecti- 

 neus, adductor longus, brevis, and magnus, and fascia lata. By its 

 deep surface with the crureus and femur. 



The CRUREUS (crus, the leg) arises from the upper border of the 

 patella, and is inserted into the front aspect of the femur, as high as 

 the anterior intertrochanteric line. When the crureus is divided from 

 its insertion, a small muscular fasciculus is often seen upon the lower 

 part of the femur, which is inserted into the pouch of synovial mem- 

 brane, that extends upwards from the knee-joint, behind the patella. 



