82 A COURSE ON ZOOLOGY. 



THE LOWER EXTREMITY. 



rotate "" thlgh ' move the 



Glutxus minimus, 



Psoas magnus, ) 



Pectineus, I raise the thigh. When the limbs are flexed, bend the 



Iliacus, body forward. 



Adductor longus, J 



Rectusfemons, ^ extend the leg. Their common tendons (quad- 



( ricepsfemoris) contain the patella. 

 Vastus externus and internus, > 



Sartorius (tailor's muscle), flexes the leg on the thigh. 

 Biceps femoris, \ 



Semi-tendinosus (30), >- flex the leg. 

 Semi-membranosus, J 



Tibialis anticus, 1 



Proprius pollute. I fl 



Gcustrocnemius (32), ) ftcting through the fendo Acmis , extend the foot. 



&OlUS) 



Extensor digitorum, j 

 Flexor digitorum, > 



Upward of twenty muscles act on the toes.) 



the extremities of the muscles are attached, and which 

 are drawn together or separated by the contractions. 



The movements of extension, as well as those of 

 flexure of the members, are produced by muscular con- 

 traction, the difference depending on the position of the 

 points of insertion of the muscles ; in the hand, for ex- 

 ample, the extensor muscles are attached to the dorsal 

 or back surfaces of the phalanges, while the flexor mus- 

 cles are attached to the interior surfaces. The contrac- 

 tions of the extensors compel the fingers to straighten 

 out, while those of the flexors bend them in against the 

 palms. Those muscles are called antagonistic of which 

 the actions are thus opposed the ones to the others, 

 and those whose actions combine to produce a common 

 movement are said to be congenerate. 



