60 LABORATORY MANUAL FOR ELEMENTARY ZOOLOGY 



(3) The ileo-fibularis is the slender muscle next to the vastus externus on 

 the dorsal side of the thigh. It extends from the ilium to the upper end of the 

 tibio-fibula, draws the thigh dorsally, and flexes the shank. 



(4) The semimembranosus is the posterior muscle of the dorsal side of the 

 thigh. It arises from the ischial symphysis, is inserted on the tibio-fibula, bends 

 the shank, and draws the leg toward the median line (adduction). 



(5) The gracilis major and minor (rectus internus major and minor in Holmes, 

 Fig. 70, p. 249) are the posterior muscles of the ventral side of the thigh on the 

 other side of the leg from the preceding. The minor is small and the most 

 posterior one. Both extend from the ischium to the knee and have the same 

 action as the preceding muscle. 



(6) The adductor magnus is the muscle next anterior to the gracilis major 

 on the ventral side. Most of it is concealed by gracilis major and the muscle 

 to be mentioned next. It originates on the ischial and pubic symphyses and is 

 inserted on the femur. It adducts the thigh and leg. 



(7) The sartorius is the flat thin muscle crossing the lower end of the adductor 

 magnus. It arises on the pubic symphysis and joins the general tendon over the 

 knee. Action, bends the shank and aducts the thigh. 



(8) The adductor longus is a thin flat muscle under the sartorius but generally 

 peeping out along the latter's anterior border. It originates on the ilium, joins 

 and acts with the adductor magnus. 



(9) The semitendinosus is a muscle of peculiar shape under the gracilis major, 

 which should be removed to see it. It has two separate tendinous heads from 

 the ischium and two separate bellies, uniting to one tendon fastened to the 

 upper end of the tibio-fibula. It acts like the gracilis major. 



ti) Muscles of the shank: 



(1) The gastrocnemius has been sufficiently described. 



(2) The peroneus is the only other muscle on the dorsal aspect of the shank. 

 It extends from the general tendon over the knee to the lower end of the tibio- 

 fibula and the ankle. It extends and twists the foot and brings the shank up 

 against the thigh, as in swimming and leaping movements. 



(3) The tibialis muscles are the small muscles of the shank lying next to the 

 bone. There are three of them. The tibialis anticus longus covers the anterior 

 surface of the tibio-fibula; it arises by a slender tendon from the lower end of the 

 femur and soon divides into two bellies, which are attached by slender tendons 

 to the ankle bones. Action, bends the ankle. Beneath the lower part of this 

 muscle is the small tibialis anticus brevis, originating on the middle of the tibio- 

 fibula, and inserted on the ankle, which it also flexes. The tibialis posticus is a 

 long slim muscle on the ventral aspect of the shank, between the gastrocnemius 

 and the tibio-fibula, to which it is attached along its entire length. It is likewise 

 inserted on the ankle, which it flexes and twists. 



(4) The extensor cruris is a small muscle on the anterior aspect of the shank, 

 lying next to the upper two-thirds of the tibio-fibula and in contact dorsally 



