I.] THE FROG. 75 



2. The superficial muscles on the front of the thigh. 



a. The sartorius : a thin ribbon-like muscle running 

 down the middle ; it arises from the symphysis 

 pubis and is inserted into a tendinous expansion 

 (aponeurosis] on the inner side of the knee-joint. 



b. The rectus internus major: a large muscle running 

 along the whole inner side of the thigh; arises 

 from the symphysis pubis below the sartorius and 

 is inserted into the same aponeurosis as that 

 muscle. 



c. The rectus internus minor: a thin muscle lying in- 

 side and rather behind the rectus internus major. 

 It arises from the pelvis close to the anus and is 

 inserted into the aponeurosis about the knee-joint. 



d. The triceps femoris : a powerful muscle on the outer 

 side of the thigh (it may be best studied later). 



3. The deep muscles of the front of the thigh. Cut 

 across the belly of the sartorius, and turn its ends 

 out of the way ; there will thus be laid bare 



a. The adductor magnus: a powerful muscle lying im- 

 mediately above the rectus internus; it arises from 

 the pelvis, between the origin of the sartorius and 

 that of the rectus internus major. Its fibres are 

 inserted directly (i.e. without the intervention of a 

 specialised tendon) into the inner side of the distal 

 half of the femur. 



b. The adductor longus: a thin band immediately in- 

 ternal to the sartorius; it arises from the anterior 

 border of the symphysis pubis and joins the ad- 

 ductor magnus at its insertion. 



