510 THE MUSCLES AND FASCIAE. 



Relations. By its superficial surface, with the Rectus, the Tensor vaginae 

 femoris, the fascia lata, and the Gluteus maximus, from which it is separated by 

 a synovial bursa ; by its deep surface, with the Crureus, some large branches of 

 the external circumflex artery and anterior crural nerve being interposed. 



The Vastus internus and Crureus are so inseparably connected together as to 

 form but one muscle, as which it will be accordingly described. It is the smallest 

 portion of the Quadriceps extensor. The anterior portion of it, covered by the 

 Rectus, is called the Crureus ; the internal portion, which lies immediately 

 beneath the fascia lata, the Vastus internus. It arises by an aponeurosis, which 

 is attached to the lower part of the line that extends from the inner side of the 

 neck of the femur to the linea aspera, from the inner lip of the linea aspera, 

 from the ridge leading from the linea aspera to the internal condyle and internal 

 intermuscular septum. It also arises from nearly the Avhole of the internal, 

 anterior, and external surfaces of the shaft of the femur, limited, above, by the line 

 between the two trochanters, and extending, below, to within the lower fourth of 

 the bone. From these different origins the fibres converge to a broad aponeurosis 

 which covers the anterior surface of the middle portion of the muscle (the Crureus) 

 and the deep surface of the inner division of the muscle (the Vastus internus), and 

 which gradually narrows down to its insertion into the patella, where it blends with 

 the other portions of the Quadriceps extensor. The muscular fibres of the Vastus 

 internus extend lower down than those of the Vastus externus, so that the capsule 

 of the joint is less covered with muscular fibres on the outer than on the inner 

 side. 



Relations. By its superficial surface, with the Psoas and Iliacus, the Rectus, 

 Sartorius, Pectineus, Adductors, and fascia lata, femoral vessels, and saphenous 

 nerve ; by its deep surface, with the femur, Subcrureus, and synovial membrane 

 of the knee-joint. 



The student will observe the striking analogy that exists between the Quadri- 

 ceps extensor and the Triceps muscle in the upper extremity. So close is this 

 similarity that M. Cruveilhier has described it under the name of the Triceps 

 femoralis. Like the Triceps extensor cubiti, it consists of three distinct divisions, 

 or heads : a middle or long head, the Rectus, analogous to the long head of the 

 Triceps, attached to the ilium, and two other portions, which may be called the 

 external and internal heads of the Triceps femoralis. These, it will be noticed, 

 are strictly analogous to the outer and inner heads of the Triceps in the arm. 



The tendons of the different portions of the Quadriceps extensor unite at the 

 lower part of the thigh, so as to form a single strong tendon which is inserted 

 into the upper part of the patella. More properly, the patella may be regarded as 

 a sesamoid bone, developed in the tendon of the Quadriceps, and the ligamentum 

 patellae, which is continued from the lower part of the patella to the tuberosity of 

 the tibia, as the proper tendon of insertion of the muscle. A synovial bursa, the 

 post-patellar bursa, is interposed between the tendon and the upper part of the 

 tuberosity of the tibia ; and another, the prepatellar bursa, is placed over the 

 patella itself. This latter bursa often becomes enlarged, constituting " housemaid's 

 knee." 



The Subcrureus is a small muscle, usually distinct from the Crureus, but occa- 

 sionally blended with it, which arises from the anterior surface of the lower part 

 of the shaft of the femur, and is inserted into the upper part of the cul-de-sac of 

 the capsular ligament which projects upward beneath the Quadriceps for a variable 

 distance. It sometimes consists of two separate muscular bundles. 



Nerves. The Tensor vaginae femoris is supplied by the superior gluteal nerve ; 

 the other muscles of this region by branches from the anterior crural. 



Actions. The Tensor vaginae femoris is a tensor of the fascia lata ; continuing 

 its action, the oblique direction of its fibres enables it to abduct and to rotate the 

 thigh inward. In the erect posture, acting from below, it will serve to steady the 

 pelvis upon the head of the femur, and by means of the ilio-tibial band it steadies 

 the condyles of the femur on the articular surfaces of the tibia, and assists the 



