THE FROG. 77 



from the hinder edge of the iliac bone. Cut it 

 across and reflect the two halves. 



ft. The vastus intsrnus: its inner head; a very 

 large muscle on the outer anterior aspect of the 

 thigh, arising from the pelvis close to the hip- 

 joint; it unites with a. to form a common 

 tendon of insertion into the aponeurosis on the 

 front of the os cruris. 



y. The rectus femoris anticus: its middle head; a 

 small muscle arising from the postero-ventral 

 border of the iliac bone and inserted along with 

 the above. 



b. The biceps femoris: a long thin muscle, lying 

 along the inner side of the vastus externus; it 

 arises from the iliac bone above the acetabulum; 

 below it divides into two slips, one of which is 

 inserted into 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. 



c. The semimembranosus: a large muscle immediately 

 below the biceps; it arises from the upper pos- 

 terior part of the iliac symphysis and is inserted 

 into the aponeurosis round the knee-joint. 



The deep muscles of the back of the thigh. 



Divide and reflect the biceps femoris and semi- 

 membranosus ; there will thus be exposed : 



a. The ghitczus : a short thick muscle arising from 

 the hinder two-thirds of the external border of 

 the ilium ; it runs down between the vastus ex- 

 ternus and the rectus anticus to be inserted, by a 



