QUADRICEPS EXTENSOR 307 



fourth lumbar nerves), l)y several l)ranehes which enter the internal surface of the 

 muscle in the upjxT tliinl of the thigh. 



Action and relations. — These will be considered with those of the two follow- 

 ing muscles. 



(c, d) Vastus Ixternus and Crureus 



The vastus internus and crureus are so closely blended that it is better to 

 describe their origins together Itefore mentioning the way in which they may be 

 separated. They have received their names, the former from its size and position; 

 the latter from its intimate connexion with the whole of the front of the thigh bone, 

 the term ' cms ' being often used synonymously with the femur. The blended 

 nniscle is a somewhat fusiform sheet which is so curved laterally as to form a 

 cylinder embracing the Avhole of the front and sides of the shaft of the femur. 



Origin. — (1) The outer lip of the lower half of the linea asperaand its external 

 bifurcation, together with the adjacent external intermuscular septum; (2) the 

 lower part of the anterior intertrochanteric line and the spiral line of the femur; 

 (3) the inner lip of the whole length of the linea aspera and its internal bifurcation, 

 together Avith the adjacent part of the internal intermuscular septum, and the front 

 of the tendon of the adductor magnus; (4) the greater part of the front and sides of 

 the femur within the limits formed l:)y the three preceding attachments and the 

 origin of the vastus externus. 



Insertion. — (1) The front aspect of the upper border of the patella immedi- 

 ately Ijehind the insertion of the rectus femoris tendon; (2) the upper half of the 

 inner border of the patella; (3) by a strong aponeurosis into the front of the inner 

 tuberosity of the tiVjia and into the adjacent deep fascia of the leg. 



Structure. — The fibres of this large muscle arise fleshy from the surface of the 

 femur and converge, from the outer side downwards, forwards, and inwards; from 

 the front directly downwards; from the inner side downwards, forwards, and out- 

 wards, upon the back and sides of a strong aponeurosis which covers the front of 

 the muscle from about the middle of the thigh downwards. The filjres which arise 

 from the tendon of the adductor magnus and the adjacent intermuscular septum 

 form the lowest part of the thick muscular belly of the vastus internus, and are 

 directed almost transversely outwards to get to their insertion upon the inner border 

 of the patella. The substance of the muscle is arranged in layers which wrap round 

 the front and sides of the femur; and betw^een the attachment of these layers to 

 the bone, longitudinal strips of bone may be found upon dissection without any 

 muscular attachment. The deepest of these layers in the lower fourth of the thigh 

 forms a separate sheet of muscular fibre, sometimes called the subcrureus, which 

 is inserted into the upper reflexion of the synovial membrane of the knee-joint. 

 Beneath this muscle is the bursa underneath the C}uadriceps, Avhich in the adult 

 connnunicates with the upper part of the knee-joint. 



A somewhat arbitrary division may be made between the vastus internus and 

 crureus by dissecting at the lower third of the thigh in a line with the inner border 

 of the patella. ^Vith a few touches of the scalpel a longitudinal separation may be 

 made clear, which extends upwards to the lower part of the anterior intertro- 

 chanteric line. The part of the muscle external to this line is the crureus, and the 

 part internal the rnsfns iufrrn'is. 



The ligamentum patellae may lie looked upon as the common tendon of the 

 quadriceps. It is a Ijand of lil)rous tissue about an inch (2"5 cm.) broad by one- 

 quarter of an inch (Gnmi.) thick, and two or three inches (5 to 7 '5 cm.) in 

 length, which is attached above to the apex and to the hiwer part of the jjosterior 

 surface of the patella; and, after passing downwards and very slightly outwards, 

 it is inserted into the anterior surface of the tubercle of the tibia. Attached to 

 its sides are strong aponeuroses by which the lower fibres of the vastus externus 

 and vastus internus and the ilio-tibial band are inserted into the tuberosities of the 

 tibia, and which Ijlend on their deep surface with the lower part of the capsule of 

 the knee-joint. 



Nerve-supply. — Xumerous branches from the anterior crural are distrilnited 

 to the upper half of the front of the crureus muscle and to the inner surface of tlie 

 vastus internus at the junetiim of the middle and lower thirds of the thigh, the 



