COMPARATIVE ANATOMY 35 



triangle (a landmark of importance In human anatomy). The 

 sartorius originates from the ventral border of the ilium, and 

 is inserted on fascia proximal to the patella, on the patella, and 

 on the proximal portion of the tibia. 



Action: to adduct and rotate the thigh, and to extend the 

 shank. 



2. Gracilis. — This broad flat muscle occupies most of the 

 medial surface of the thigh not covered by the sartorius. It 

 originates by a strong tendon from the caudal three-fourths of 

 the pubic symphysis. Part of this tendon Is common to the 

 gracilis muscles of both legs and also gives origin to some fibers 

 of the adductor femoris muscles of both legs. The gracilis 

 inserts by a thin aponeurosis on fascia on the shank and on the 

 medial side of the proximal end of tibia. 



Action: to adduct and extend the thigh; to flex the shank. 



Extending across Scarpa's triangle are the femoral artery 

 (Injected with yellow coloring material) , femoral vein (dark), and 

 the femoral nerve (white). If traced toward the foot each will 

 be found to give off many branches to the muscles. 



Turn the cat over. If the superficial fascia has been cleanly 

 removed, several muscles will be exposed. 



3. Biceps Femoris. — This is a large triangular muscle cover- 

 ing the caudal two-thirds of the lateral surface of the thigh. It 

 is narrow at the proximal end and widens distally. Before dis- 

 secting It, read about the next muscle, the tenuisslmus, which 

 adheres closely to the underside of the biceps femoris and may 

 be easily destroyed. The biceps femoris originates from a small 

 area on the posterior end of the Ischium; insertion Is on the lateral 

 margin of the patella and by means of fascia, on the tibia. 

 Separate this muscle from the surrounding tissues, being careful 

 not to Injure other muscles or their tendons. Carefully cut it 

 transversely through the middle and expose the tenuisslmus 

 muscle and the large sciatic nerve. 



Action: to abduct the thigh and flex the shank. 



4. Tenuissimus. — ^Thls Is an extremely slender muscle, 

 beneath and closely adherent to the biceps femoris. It Is easily 

 overlooked. It originates from the transverse process of the 

 second caudal vertebra, passes to the caudal border of the biceps 

 femoris, and Is Inserted by the same fascia on the tibia. 



