THE FROG. 221 



a. The vastus internus: the anterior division, 

 which has been already seen on the front of 

 the thigh. (2. d. 97.) 



fB. The vastus externus : the posterior division ; it 

 arises from the hinder edge of the iliac bone. 



7. The rectus femoris anticiis : the middle division 

 of the triceps ; it arises from the posterior part 

 of the ventral border of the iliac bone. For the 

 insertion of the triceps femoris, see 2. d. rj. 



b. The glutceus : this muscle arises from the hinder 

 two-thirds of the external surface of the ilium ; 

 it runs down between the vastus externus and 

 the rectus anticus to be inserted into the back of 

 the head of the femur. 



c. The pyriformis. This arises from the posterior 

 part of the urostyle and, passing inside- the vastus 

 externus, is inserted inta the shaft of the femur. 



d The biceps femoris : a long thin muscle, lying 

 along the inner side of the vastus externus ; it 

 arises, from the iliac bone above the acetabu- 

 lum; below, it divides, into two pieces, one of 

 which is inserted inta the- middle of the shaft 

 of the femur, while the other ends in a rounded 

 tendon which is inserted into the back of the 

 distal end of the same bone. 



e. The semimembranosus ; a large muscle inside the 

 biceps; it arises from the upper posterior part 

 of the iliac symphysis and is inserted into the- 

 aponeurosis round the knee-joint. 



Lying deep in the thigh, between the biceps, 

 and semimembranosus muscles, will be seen the 

 femoral vessels and the sciatic nerve. 



