MUSCLES OF THE PELVIC LIMBS. 203 



with the sartorius (Fig. 91, a) and the structures in the ilio- 

 pectineal fossa. Cranial (or dorsal) surface with the rectus 

 femoris (Fig. 92, b] and vastus intermedius. Caudal (ventral) 

 surface with the pectineus (Fig. 92, e), adductor longus (Fig. 

 92,/), adductor femoris (Fig. 92, ), and semimembranosus 

 (Fig. 92, /*). 



(4) M. vastus intermedius. A flat mass of muscle which 

 lies beneath the rectus femoris. 



Origin from nearly the whole of the dorsal surface of the 

 shaft of the femur between the areas for the vastus medialis and 

 vastus lateralis. The area of origin extends distad to an 

 oblique line the middle of which is about one and one-half 

 centimeters from the patellar surface, the lateral border of the 

 area being longer than the medial border. 



Insertion by muscle-fibres into the capsule of the joint. 

 The central fibres are inserted about one centimeter proximad 

 of the patella, while the lateral mass passes to the level of the 

 proximal end. 



Relations. Outer surface with- the rectus femoris (Fig. 

 92, b}\ borders with the vastus medialis (Fig. 92, c] and vastus 

 lateralis (Fig. 90, d}; inner surface with the femur. 



Action. The quadriceps extensor is an extensor of the 

 shank. The vastus intermedius acting separately is a tensor 

 of the capsule of the knee-joint. 



3. Muscles of the Lower Leg (Crus). 



A. ON THE VENTRAL SIDE. M. gastrocnemius. This 

 is the great muscular mass of the calf. It arises by two heads, 

 the caput laterale or lateral head (Fig. 90, ;), and the caput 

 mediale or medial head (Fig. 91, /), of the gastrocnemius. 



Caput laterale (Fig. 90, ?, ;', m"). The origin of the 

 lateral head is in four portions: 



(1) From the tendon of origin of the plantaris which comes 

 from the middle of the lateral border of the patella. The ten- 

 don ends in a small conical mass of fibres (;') which joins the 

 ventral part of the common head. 



(2) By a slender flat tendon, distad of the first, from the 



