THE MUSCLES OF THE LOWER EXTREMITY. 173 



It arises from a point just below the head of the femur 

 on the postei'o-interual aspect of the shaft, and is attached 

 down the bone in a straight line, increasing in width as 

 it nears the knee, as low as the internal condyle. It then 

 clears the joint to become inserted as a rather broad 

 tendon along the thickened inner border of the summit of 

 the tibia. This muscle is pointed above, and its fibres 



Fig. 48. — Thigli of Touraco {Corythaix erythrolojjha) viewed from the inner side, 

 to show the ambiens muscle, arising from the prtepubic spine of the 

 pelvis (p), and running along to blend with one of the tendons of origin 

 of the flexor perforatus digitorum (f.p.). F, femur ; Pi, patella ; i.e., 

 inner condyle of femur ; t, tibia ; b, biceps (cut short) ; s, sartorius 

 (also cut) ; e, e, extensor femoris ; sm, semimembranosus ; add, 

 adductores. N.B.- — The surrounding parts have been .somewhat dis- 

 torted from their natural positions to show better the course of the 

 ambiens. (By the author, after Forbes.) 



diverge as they descend, thus forming a subconical mus- 

 cular mass, which stands out prominently from the femoral 

 shaft. The lower and outer aspect of the muscle is ten- 

 dinous, which tendon in passing down merges with its 

 tendon of insertion into the tibial head. 



The vastus internus also constitutes one of the 

 extensors of the leg upon the knee, and is a powerful 

 auxiliary to the extensor femoris. 



