60 A MANUAL OF ZOOLOGY 



separating these two surfaces, the upper is the dorsal or 

 superior, and the under is the ventral or inferior surface. 



The Superficial IVIuscles of the Ventral Surface — The 

 sartorius extends along the entire length of the femur ex- 

 ternal to the middle of the ventral surface. Its origin is 

 on the symphysis of the ilium and it is inserted on the 

 inner tuberosity of the tibio-fibula and in the aponeurosis 

 of the_ knee joint. One of the largest muscles of the thigh 

 is the adductor magnus. It runs along the inner border 

 of the sartorius under which it dips at the distal end. It 

 originates on the pubis and the ischium Und is inserted on 

 the distal end of the femur together with the adductor 

 longus. External to and mostly covered by the sartorius 

 is the adductor longus. It is a ribbon shaped muscle be- 

 tween the sartoi'ius and the vastus internus. Its origin 

 is on the ilium anterior to the acetabulum and it is in- 

 serted with the preceding muscle. The rectus internus 

 major is a large muscle situated internal to the origin of 

 the adductor magnus and the insertion of the sartorius. 

 What la its origin and its insertion? The rectus Internus 

 minor lies internal to the rectus internus major on its ven- 

 tral border. Its origin is on the symphysis of the ischium 

 and is inserted on the inner side of the tibio-fibula just 

 below its head. 



Deep Muscles of the Ventral Surface of the Thigh — 

 The semitendinosus arises by two heads, one on the sym- 

 physis of the ischium and the other on the symphysis pubis. 

 The two heads unite near the middle of the femur and 

 are inserted into the knee joint and the proximal inner 

 surface of the tibio-fibula. The pectin eus has its origin 

 on the symphysis pubis and is inserted on the proximal 

 ha:if of the posterior border of the femur. This muscle is 

 dorsal to the vastus internus and the adductor magnus. 

 Internal to the pectineus and dorsal to the adductor mag- 

 nus is a short broad muscle, the adductor brevls. Its orig- 

 in is on the symphysis pubis and the ischium posterior to 

 that of the pectineus. 



Superficial Muscles of the External Surface of the 

 Thigh — The triceps extensor femorls lies on the external 

 surface of the thigh. It originates by three heads: 

 vastus externus, vastus internus, and the rectus anticus 



