72 THE MUSCULAR SYSTEM OF THE FROG. 



1. Muscles of the thigh. 



Remove the skin from one of the legs of the frog ^ and clean the 

 muscles first of the j)reaxial and then of the i^ostaxial surfaces. 



a. Superficial muscles of the preaxial (apparent ventral) 



surface of the thigh. 



i. The sartorius is a long narrow muscular band which 

 crosses the thigh somewhat obliquely from the 

 outer to the inner side. It arises from the iliac 

 symphysis below the acetabulum, and is inserted 

 into the inner side of the head of the tibia. 



ii. The adductor magnus is a large muscle lying along 

 the inner border of the sartorius, but passing 

 beneath it at its distal end. It arises from the 

 pubic and ischial symphyses, and passes under 

 the sartorius to be inserted into the distal third 

 of the femur. 



iii. The adductor longus is a long narrow muscle lying 

 along the outer side of the adductor magnus, 

 and often completely hidden by the sartorius: 

 it arises from the iliac symphysis beneath the 

 sartorius, and unites a little way beyond the 

 middle of the thigh with the adductor magnus. 



iv. The rectus internus major is a large muscle lying 

 along the inner side of the adductor magnus 

 and of the sartorius. It arises from the ischial 

 symphysis and is inserted into the head of the 

 tibia. 



V. The rectus internus minor is a narrow flat band of 

 muscle running along the inner, or flexor margin 

 of the thigh : it arises from a tendinous expansion 

 connected with the ischial symphysis, and is 

 inserted into the inner side of the tibia, just 

 below its head. 



b. Superficial muscles of the extensor surface of the thigh. 



i. The triceps extensor femoris, the great extensor 

 muscle of the thigh, arises by three distinct 

 origins, which will be described separately, and 

 is inserted into the tibia just below its head. 



