62 THE ANATOMY OF THE HORSE. 



of the obturator nerve will be found entering its deep face, after having 

 passed through the obturator externus muscle. Other branches of the 

 same nerve will be found supplying the small adductor and the pectineus. 



The Femoral Artery (Plate 14). The remaining portion of this 

 vessel is now exposed as it winds round behind the shaft of the femur, 

 leaving its impress on the bone. It is seen passing in between the 

 heads of the gastrocnemius muscle, at which point it takes the name of 

 popliteal. In this part of its course it gives off only one vessel of note — 

 the femoro-popliteal. 



The Femoro-popliteal Artery. The point of origin of this branch 

 marks the lower limit of the femoral artery. It passes backwards in a 

 horizontal direction, and penetrates the semitendinosus. Near its origin 

 it gives off a considerable branch which ascends behina the femur, sup- 

 plying the biceps, and anastomosing with the profunda. Other branches 

 descend from it to the gastrocnemius. 



Popliteal Lymphatic Glands. These will be found on the track 

 of the femoro-popliteal artery between the semitendinosus and biceps 

 femoris muscles. 



The Profunda or Deep Femoral Artery. In the preceding stage 

 of the dissection this branch of the femoral was seen at its origin. 

 It passes downwards and backwards, between the adjacent edges of 

 the iliacus and obturator externus, and under cover of the pectineus 

 and adductor parvus. Above the insertion of the quadratus femoris 

 it crosses behind the femur, where its terminal branches descend to 

 supply the biceps. It also furnishes collateral branches to the 

 pectineus, gracilis, and adductors. 



Veins. The foregoing arteries are accompanied by satellite veins of 

 the same names. 



The Quadratus Femoris (Plates 14 and 16). This is a somewhat 

 slender riband-shaped muscle* It arises from the lower surface of 

 the ischium in front of the tuberosity, and it becomes inserted into 

 .an oblique line on the back of the femur, at the level of the third 

 trochanter. 



Action. — It is an extensor and outward-rotator at the hip. 



The Obturator Externus (Plate 14). This muscle, which is coarsely 

 fasciculated, covers the obturator foramen, and conceals the obturator 

 nerves and vessels as they emerge from the pelvis. It is traversed by 

 two branches of the obturator nerve, the posterior of which is for the 

 great adductor, while the anterior splits into branches for the supply 

 of the small adductor, pectineus, and gracilis. It arises from the lower 

 surface of the pubis and ischium, and is inserted into the trochanteric 

 fossa. 



Action. —It is an extensor and outward-rotator at the hip. 



Directions. — The nerves which emerge from the obturator externus 



