MUSCLES OF THE HIND-LIMB 65 



d. Deep muscles of the thigh. 



Lay the frog on its back and dissect the thigh from the pre- 

 axial surface. Separate the adductor magnus and the rectus 

 interims major with blunt instruments so as to expose the follow- 

 ing muscles : 



i. The semitendinosus is a long thin muscle which 

 arises by two heads ; an anterior one from the 

 ischium close to the ventral angle of the ischial 

 symphysis and the acetabulum ; and a posterior 

 one from the ischial symphysis. The anterior 

 head passes through a slit in the adductor 

 magnus and unites with the posterior head in 

 the distal third of the thigh. The tendon of 

 insertion is long and thin, and joins that of the 

 rectus interims minor to be inserted into the 

 tibia just below its head. 



Divide the adductor magnus and the sartorius in the middle 

 and turn the cut ends backwards and forwards, so as to expose 

 the following muscles : 



ii. The adductor brevis is a short wide muscle, lying 

 beneath the upper end of the adductor magnus. 

 It arises from the pubic and ischial symphyses, 

 and is inserted into the preaxial surface of the 

 proximal half of the femur. 



iii. The pectineus is a rather smaller muscle, lying 

 along the outer (extensor) side of the adductor 

 brevis. It arises from the anterior half of the 

 pubic symphysis in front of the adductor brevis, 

 and is inserted like it into the proximal half of 

 the femur. 



iv. The ilio-psoas arises by a wide origin from the 

 inner surface of the acetabular portion of the 

 ilium : it turns round the anterior border of the 

 ilium, and crosses in front of the hip-joint, where 

 for a short part of its course it is superficial 

 between the heads of the vastus internus and of 

 the rectus anticus femoris : it then passes down' 

 the thigh beneath these muscles, and is inserted 

 into the back of the proximal half of the femur. 



K 



