COMPARATIVE ANATOMY OF THE MUSCULAR SYSTEM 153 



k) Adductor longus and adductor magnus. Cut through the middle of the 

 gracilis and find beneath it two stout muscles, their fibers running from the 

 median ventral line to the femur. The anterior muscle is the adductor longus; 

 the posterior one, the adductor magnus. Origin, various parts of the ischium; 

 insertion, femur; action, adductors of the thigh. 



/) Semitendinosus. Split open the adductor magnus and find inside of it 

 a cylindrical muscle, the semitendinosus. Origin, ischial tuberosity; insertion, 

 medial condyle of the tibia; action, flexor of the shank. 



m) Semimembranosus. This is the muscle which forms the posterior margin 

 of the thigh, between the biceps femoris and the adductor magnus. Origin, 

 fascia over the biceps, and ischial tuberosity; insertion, with the gracilis in the 

 fascia of the shank; action, flexor of the shank, 

 t: 



a) Tensor fasciae latae. Examine the lateral (outer) surface of the thigh. 

 The anterior part of this is covered by a tough fascia, the fascia lata. In the 

 dorsal part of this is a muscle, the tensor fasciae latae, a thick triangular muscle. 

 Origin, ilium and neighboring fascia; insertion, fascia lata; action, tightens the 

 fascia lata. 



b) Biceps femoris. This is the large muscle on the lateral surface of the 

 thigh posterior to the fascia lata and covering more than half of the surface of 

 the thigh. It has but one head in the cat. Origin, tuberosity of the ischium; 

 insertion, patella and tibia by a tendon, and the fascia of the shank; action, abduc- 

 tor of the thigh and flexor of the shank. 



c) Caudofemoralis. Clean away the fascia from the back in front of the 

 base of the tail, as far forward as the anterior end of the pelvic girdle. Muscles 

 will be found between the median dorsal line and the thigh. The most posterior 

 of these is the narrow flat caudofemoralis, passing from the side of the root of 

 the tail toward the dorsal end of the biceps femoris. Origin, transverse processes 

 of the second and third caudal vertebrae; insertion, the muscle passes ventrally 

 concealed by the anterior margin of the biceps femoris. This should be lifted 

 up and the caudofemoralis followed to its tendon; the latter is very long and 

 passes to the patella on which it is inserted. Action, abductor of the thigh, exten- 

 sor of the shank. 



d) Gluteus maximus. A rather thin flat muscle immediately anterior to 

 the preceding. It is imbedded in the fascia and is continuous with the tensor 

 fasciae latae anteriorly. Origin, from the fascia and from the transverse processes 

 of the last sacral and first caudal vertebrae ; insertion, fascia lata and to a slight 

 extent on the greater trochanter; action, in common with the next. 



e) Gluteus medius. The very large triangular muscle immediately in front 

 of the preceding and partly covered by it. The gluteus maximus should be 

 cut across to see it. Origin, adjacent fascia, crest of the ilium, and lateral surface 

 of the ilium, and transverse processes of the last sacral and first caudal vertebrae; 



