B2 GENERAL BIOLOGY 



3. The muscles of the Wrist and Fingers are numerous and com- 

 plicated. 



Innervation: Branches and twigs of II spinal or Brachial 

 nerves innervate all arm and finger muscles. 



D. MUSCLES OiF THE HIND-LIMB 



(1) Superficial muscles of the Thigh on the Preaxial (apparent 

 ventral)* Surface. 



1. Sartorius ( ), a long, narrow band arising 

 from the lower end of the ilium, lying obliquely upon the adductor mag- 

 nus, and inserted into the tibia on its inner side near the end. It bends 

 the knee. 



2. Adductor magnus, a large muscle arising from the pubis and 

 ischium, lying along the inner border of the sartorius and inserted into 

 the femur near its lower end. It draws the thigh towards the body. 



3. Adductor longus is a long narrow muscle lying along the outer 

 side of the adductor magnus, and often completely hidden by the sar- 

 torius ; it arises from the iliac symphysis beneath the sartorius, and unites 

 a little way beyond the middle of the thigh with the adductor magnus. 

 It adducts the thigh and draws it ventrally. 



4. Gracilis major ( ) or rectus internus major, 

 a large muscle arising from the ischium, lying along the inner side of the 

 adductor magnus, and inserted into the inner-side of the head of the 

 tibia. It bends the knee. 



5. Gracilis minor or rectus internus minor is a narrow flat band of 

 muscle running along the inner, or flexor margin of the thigh ; it rises 

 from a tendinous expansion connected with the ischial symphysis, and is 

 inserted into the inner side of the tibia, just below its head. Action is 

 the same as for gracilis major. 



Innervation: Branches and twigs from the sciatic nerve and 

 plexus. 



(2) Superficial muscles of the Extensor Surface of the Thigh. 



1. Triceps extensor femoris, or cruris, a very large muscle in- 

 serted into the front of the tibia just below the head of the latter, but 

 arising from the pelvic girdle as three separate muscles, the rectus an- 

 terior femoris ( ), vastus externus ( ), 

 and vastus internus, or crureus ( ). All these lie 

 on the front of the thigh, and their action is to straighten the knee. 



Innervation: Branches and twigs from the sciatic nerve and 

 plexus. 



(3) Superficial muscles of the postaxial (apparent dorsal) Surface 

 of the Thigh. 



*The femur of the frog rotates away from the midline more than does the femur of man. 

 Consequently the true outer border of the frog's thigh is equivalent to the inner border of man's. 

 In other words the preaxial surface of the frog's thigh is equivalent to the inner surface of man s. 



