82 DISSECTION OF THE DOG 



M. obturator externus. — The external obturator muscle covers the 

 ventral aspect of the obturator foramen. Its origin is from the ventral surface 

 of the pubis and ischium about the margin of the foramen. The fibres of the 

 muscle converge laterally to be inserted into the trochanteric fossa. 



M. qtjadrattts fbmoris. — The quadrate femoral muscle is short and thick. 

 Arising from the ventral surface of the sciatic tuber, it is inserted into the distal 

 part of the trochanteric fossa on a level with the lesser trochanter. 



Dissection. — Remove the skin and fascia from the gluteal and thigh regions. 

 Observe the thickness of the fascia and the accumulation of fat con- 

 nected therewith. When all the fat has been removed, an extensive 

 sheet of fascia, covering the gluteal muscles and the anterior surface of 

 the thigh, is revealed. Removal of the gluteal fascia is rendered tedious 

 from the fact that its deep face affords origin to the gluteal muscles. The 

 fascia of the thigh is known as the fascia lata and is intimately connected 

 with the biceps and tensor fasciae latse muscles. 



M. tensor eascxsi lam:. — The tensor muscle of the broad fascia of the thigh 

 is the most oral of the group now exposed, and can be readily separated into 

 two parts. Arising from the ventral border of the ilium and the middle 

 gluteal muscle, its fibres radiate and give place to an aponeurosis which joins 

 the superficial gluteal, biceps and quadriceps muscles, thus obtaining an 

 attachment to the patella. In addition, some fibres are inserted into the 

 intermuscular septum between the biceps and lateral vastus muscles. 

 Medial to the tensor fasciae latae is the lateral circumflex artery. 



M. gltjtjsus sttpereicialis. — The superficial gluteal muscle is not suffi- 

 ciently extensive to completely hide the middle gluteal upon which it rests. 

 The origin of the muscle is from the transverse processes of the sacrum, the 

 sacro-tuberous ligament, the first coccygeal vertebra, and the gluteal fascia. 

 Its insertion is into the trochanter tertius of the femur. Some of its apo- 

 neurotic tendon blends with the tensor fasciae latae and the fascia over the 

 lateral vastus and rectus femoris muscles. 



M. biceps femobis. — The biceps muscle is thick and powerful, covering the 

 greater part of the lateral aspect of the thigh. It arises by two heads. A large 

 fleshy head springs from the sacro-tuberous ligament and the sciatic tuber. 

 A much smaller and tendinous origin is from the tuber medial to the first- 

 mentioned origin. The muscle is inserted into the patella, patellar ligament, 

 anterior tibial crest, fascia lata, and fascia of the leg. 



Dissection. — Reflect the superficial gluteal muscle so as to expose the middle 

 gluteal completely. 



N. otTTANEtrs femobis posteeiob. — Leaving the pelvis in company with the 



