356 ZOOTOMY. 



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

 hgamentum patellae : cut through and reflect. 



(c). 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. 



{d). The short or deep head of the rectus anticus 

 {gu.-L^), 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 {qu.T,'^), 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 {qu.a,), 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 {bi), covering the posterior 

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

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

 anterior head {bP) 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-cyHndrical : the second or posterior head 

 (bi''-) arises from the posterior part of the tuber ischii in 



