MUSCLES 41 



tendon on the internal tuberosity of the tibia. 

 (Plates II., III., and IV.) 



11. The Quadriceps Extensor is composed of four 

 large muscles which have separate origins but are 

 inserted on the tuberosity of the tibia by a com- 

 mon tendon, the " tendon of the patella." 



a. The vastus externus is the largest and most 

 external of the four divisions. Its origin is on 

 the whole outer surface of the shaft of the femur 

 and on the great trochanter. (Plate III.) 



b. The rectus femoris is the most anterior of 

 the four divisions, lying between the vastus ex- 

 ternus and the muscle next to be described, the 

 vastus internus. It arises from the ilium just 

 above the acetabulum. (Plate IV.) 



c. The vastus internus lies between the rectus 

 femoris and the sartorius. It arises from the in- 

 ner and anterior side of the upper part of the fe- 

 mur. (Plate IV.) 



d. The vastus medius, the smallest division, 

 arises from the lower part of the front of the fe- 

 mur. To expose this muscle the three preceding 

 divisions must be reflected. 



12. The Pyriformis is a small triangular muscle. 

 It arises from the ventral surface of the sacrum, 

 and, passing along the posterior margin of the 

 gluteus minimus, is inserted on the great trochan- 

 ter of the femur. 



13. The Gracilis is a broad, thin muscle, cover- 

 ing the greater part of the inner side of the thigh. 



