80 DISSECTION OF THE DOG 



M. SEMiTENDiNOSUS. — This is a long and fleshy muscle lying aboral and 

 lateral to the semimembranosus, with an origin from the lateral part of the 

 sciatic tuber ; its insertion is by a strong tendon to the medial surface of the 

 tibia and the anterior tibial crest in line with the insertion of the gracilis. 



Dissection. — Cut across the semimembranosus muscle about its middle, 

 and reflect towards its origin and insertion. In turning upwards the 

 proximal part look for the nerve to the muscle, as well as for that 

 for the semitendinosus. 



The distal part of the femoral artery will be exposed as it lies in a 

 triangular channel formed by the vastus medialis, adductor, and semi- 

 membranosus muscles. 



In the depths of the groove formed by the semitendinosus, adductor, and 

 biceps muscles the sciatic nerve will be found. This divides unequally 

 into the tibial and common peroneal nerves. 



Now reflect the adductor and pectineus muscles by cutting them across 

 not far from their origins. Thus will be revealed the branches of the 

 obturator nerves supplying the adductor and pectineus, the deep 

 femoral artery, the insertion of the ilio-psoas muscle, and the external 

 obturator and quadratus femoris muscles. 



A. PROFUNDA FEMORIS. — As has previously been noted, the deep femoral 

 artery arises from the external iliac artery in common with the caudal epigastric 

 and external pudendal arteries. Immediately after its origin the artery 

 pierces the tendinous aponeuroses of the abdominal wall and arrives between 

 the ilio-psoas and pectineus muscles. From this point the artery continues 

 between the adductor and external obturator muscles. A branch passes 

 through the obturator foramen, and others supply the various adjacent muscles. 



N. OBTTJRATORius. — The obturator nerve comes out of the pelvis by the 

 obturator foramen, and appears in the thigh by crossing the oral border of the 

 external obturator muscle. It immediately divides into branches for gracilis, 

 adductor, and pectineus muscles. 



M. ILIO-PSOAS. — The insertion of the ilio-psoas muscle into the lesser tro- 

 chanter of the femur is now exposed, and the origin of its iliac portion from 

 the medial surface of the ihum and the tendon of psoas minor can be examined. 



A. CIRCXJMFLEXA FEMORIS LATERALIS ET A. FEMORIS ANTERIOR. — The lateral 



circumflex and anterior femoral arteries may arise either together or separately 

 from the femoral artery about the point at which this vessel crosses the ventral 

 border of the iHo-psoas muscle. The lateral circumflex artery runs in a cranial 

 and lateral direction between the sartorius medially and the rectus femoris 

 and tensor fasciae latae muscles laterally. It supplies these and the gluteal 

 muscles. The anterior femoral artery is much larger than the preceding, and 

 disappears almost at once between the rectus femoris and the medial vastus 

 muscles. 



