82 



GENERAL ZOOLOGY 



other from the tendon of the triceps. It terminates in a strong 

 tendon, the tendo Achillis, which after passing over the ankle 

 joint spreads out in a connective tissue sheet over the plantar 

 surface of the foot. Its contraction flexes the crus and extends 

 the foot. The tibialis anticus (Fig. 47) lying at the front of the 

 leg, originates on the distal end of the femur, its ligament passing 



B 



Fig. 49. — Fibrils (myofibrils) of the wing muscle of the wasp. A, contracted 

 fibril showing a reduction in the size of the isotropic bands and a corresponding 

 increase in the anisotropic bands; B, a stretched fibril with its anisotropic bands 

 constricted at the line of Hensen; C, an uncontracted fibril, k, membrane of 

 Krause forming the boundary of a sarcomere; Y, isotropic substance; s, aniso- 

 tropic substance; h, Hensen's line. (Adapted from Schafer, Essentials of Histology, 

 Longmans, Green & Co. By permission.) 



beneath the tendon of the triceps. This muscle divides at about 

 the middle of the leg, the inner half being inserted on the astrag- 

 alus and the outer half on the calcaneum. It extends the foot 

 and flexes the tarsus. The peroneus muscle, seen in a dorsal 

 view of the leg (Fig. 48) between the tibalis anticus and the 

 gastrocnemius, originates in a tendon attached to the distal 

 end of the femur and ligaments of the knee joint; it is inserted 



