220 ELEMENTARY BIOLOGY. [XIII. 



inserted directly {i. e. without the intervention 

 of a specialised tendon) into the inner side of 

 the distal half of the femur. 



3. The deep muscles on the front of the thigh. 



a. Divide and reflect the adductor longus, rectus 

 internus major and rectus internus minor. The 

 following muscles will be displayed : — 



a. The pectineus : it lies at the upper part of the 

 thigh immediately internal to the vastus inter- 

 nus : it arises from the front 'of the pelvis, close 

 to the symphysis, and is inserted into the 

 anterior surface of the distal half of the femur. 



/3. The 'adductor brevis (2. d. 7) : it lies along the 

 inner side of the pectineus and arises and 

 is inserted close to it. 



7. The semitendinosus : this is a long slender 

 muscle lying beneath the rectus internus major 

 and bifurcated at its upper end : its two heads, 

 thus formed, arise, on'e {anterior head) from 

 the pelvis between the ischial symphysis and 

 the acetabulum ; the other {posterior head) 

 from the ischial symphysis : the muscle termi- 

 nates below in a rounded tendon which is 

 inserted along with the sartorius. 



4. Turn the frog over on to its belly, and remove the 

 skin from the back of the limb. 



The muscles on the hack of the thigh. These are : — 



a. The triceps femoris : a very large muscle on the 

 outer side, divided above into three heads, which 

 are often regarded as separate muscles, viz. 



