78 ANATOMY OF THE WOOD RAT 



M. biceps femoris posticus (figs. 6, 32) has origin from 

 the superior tuberosity of the ischium partly deep to the 

 heads of the semitendinosus. Rapidly expanding it ex- 

 tends to an insertion upon the fascia of about half the 

 cranial border of the lower leg. 



M. tenuissimus (figs. 6, 32) is an exceedingly slender and 

 fragile muscle which is easily overlooked. Origin is from 

 the deeper dorsal fascia between the origins of the gluteus 

 superficialis and biceps anticus. It passes deep to the 

 biceps posticus and gluteus maximus, and extending distad, 

 is inserted onto the fascia of the lateral side of the calf. 



All of these six flexor muscles of the thigh are served by 

 the N. ischiaticus. 



The extensors of the thigh, numbering four and com- 

 prising the quadriceps femoris, are the 



Mm. rectus femoris vastus femoris 



vastus lateralis vastus medialis 



M. rectus femoris (figs. 7, 17, 32, 33) is a strong muscle 

 situated between the vastus lateralis and the other two 

 vasti. Arising by a single head it is pennated proximad, 

 and has origin by tendon fibers from the femoral process 

 upon the ilium immediately craniad of the acetabulum. 

 Investing aponeuroses develop upon its lateral and medial 

 belHes, and these converge to a strong insertion upon the 

 proximal border of the patella. 



M. vastus lateralis (figs. 6, 7, 17, 32) has origin by 

 tendon fibers from the disto-cranio-lateral part of the 

 great trochanter. It extends in a thick mass superficial to 

 the rectus femoris and vastus intermedins, curving slightly 

 toward the medial surface of the leg to an insertion by 

 tendon fibers onto the patella and patellar ligament. 



M. vastus femoris (or intermedins) (figs. 17, 32, 33) 

 has origin from practically the whole of the cranial border 

 of the shaft of the femur in a pennated manner. The 



