76 ELEMENTARY BIOLOGY. [CHAP. 



Force the adductors longus and magnus well apart 

 (noting the insertion of the latter) and pin them back 

 if needful; there will thus be exposed 



c. The pectineus: a small muscle, arising from the 

 front of the pelvis, close to the symphysis, and 

 inserted into the anterior surface of the distal half 

 of the femur. 



d. The adductor brevis: a small muscle lying on the 

 inner side of the pectineus, close to which it arises 

 and is inserted. 



Sever the rectus internus major and r.i. minor and 

 turn their cut ends back; thrust the adductor magnus 

 forwards; there will thus be laid bare 



e. The semitendinosus ; this is a long slender muscle 

 bifurcated at its upper end: its two heads, thus 

 formed, arise, one (anterior head) from the pelvis 

 between the ischial symphysis and the aceta- 

 bulum ; the other (posterior head} from the ischial 

 symphysis: the muscle terminates below in a 

 rounded tendon which is inserted along with the 

 sartorius. 



Its anterior head enters into a close relationship 

 with the adductor magnus. 



4. The superficial muscles on the back of the thigh. 



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

 skin from the back of the limb. 



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. 



a. The vastus extcrmts: its outer head; it arises 



