356 ZOOTOMY. 



neck of the femur, and at its distal end joins the rectus in the 

 ligamentum patellae : cut through and reflect. 



(f). The principal or superficial head of the vastus 

 externus (^.3), situated just posterior to the rectus 

 anticus on the outer surface of the thigh : it is the largest 

 head of the quadriceps : it arises from the neck of the femur 

 and from the great trochanter, and passes distally into the 

 common tendon of the quadriceps or ligamentum patellae. 



The short or deep head of the rectus anticus 

 1 ), a cylindrical muscle lying along the inner or pre-axial 

 side of the vastus externus, by which it is partly enwrapped : 

 it arises from the posterior part of the pubic border of the 

 ilium, and passes distally into the common tendon of the 

 quadriceps. 



(e). The accessory or deep head of the vastus 

 externus (^^3 1 ), a flattish muscle, lying between the 

 concave inner face of the superficial head and the crureus 

 (see below) : it arises from the femur close to the origin of 

 the superficial head, and distally joins the ligamentum 

 patellae : cut through and reflect both heads of the vastus 

 externus and the short head of the rectus. 



(/). The crureus (^#.4), arising from the shaft of the 

 femur, the anterior (dorsal) surface of which it covers, and 

 passing distally into the commom tendon of insertion of the 

 quadriceps : detach it from its origin and reflect. 



441. The biceps femoris (/;/), covering the posterior 

 half of the outer side of the thigh and forming the chief 

 flexor of the cms : it has two heads, of which the first or 

 anterior head (bi l ) arises by a wide flat tendon from the 

 three posterior sacral and the three anterior caudal vertebrae, 

 and passes outwards, gradually diminishing in breadth and 

 becoming sub-cylindrical : the second or posterior head 

 arises from the posterior part of the tuber ischii in 



